Big Data and Hadoop Interview Questions and Answers

What is BIG DATA?

Big Data represents a huge and complex data that is difficult to capture, store, process, retrieve and analyze with the help of on-hand traditional database management tools.


What are the three major characteristics of Big Data?

According to IBM, the three characteristics of Big Data are:

Volume: Facebook generating 500+ terabytes of data per day.

Velocity: Analyzing 2 million records each day to identify the reason for losses.

Variety: images, audio, video, sensor data, log files, etc.


What is Hadoop?

Hadoop is a framework that allows distributed processing of large data sets across clusters of commodity hardware(computers) using a simple programming model.


What is the basic difference between traditional RDBMS and Hadoop?

Traditional RDBMS is used for transactional systems to store and process the data, whereas Hadoop is used to store and process large amount of data in the distributed file system.


What are the basic components of Hadoop?

HDFS and MapReduce are the basic components of hadoop.

HDFS is used to store large data sets and MapReduce is used to process such large data sets.


What is HDFS?

HDFS stands for Hadoop Distributed File System and it is designed for storing very large files with streaming data access patterns, running clusters on commodity hardware.


What is Map Reduce?

Map Reduce is a java based programming paradigm of Hadoop framework that provides scalability across various Hadoop clusters


How Map Reduce works in Hadoop?

MapReduce distributes the workload into two different jobs namely 1. Map job and 2. Reduce job that can run in parallel.

1.The Map job breaks down the data sets into key-value pairs or tuples.

2.The Reduce job then takes the output of the map job and combines the data tuples into smaller set of tuples.


What is a Name node?

Name node is the master node on which job tracker runs and consists of the metadata. It maintains and manages the blocks which are present on the data nodes. It is a high-availability machine and single point of failure in HDFS.


What is a Data node?

Data nodes are the slaves which are deployed on each machine and provide the actual storage. These are responsible for serving read and write requests for the clients.


What is a job tracker?

Job tracker is a daemon that runs on a name node for submitting and tracking MapReduce jobs in Hadoop. It assigns the tasks to the different task tracker. In a Hadoop cluster, there will be only one job tracker but many task trackers. If the job tracker goes down all the running jobs are halted.


How job tracker works?

When a client submits a job, the job tracker will initialize the job and divide the work and assign them to different task trackers to perform MapReduce tasks.


What is a task tracker?

Task tracker is also a daemon that runs on data nodes. Task Trackers manage the execution of individual tasks on slave node.


How task tracker works?

Task tracker is majorly responsible to execute the work assigned by the job tracker and while performing this action, the task tracker will be simultaneously communicating with job tracker by sending heartbeat.


What is Heart beat?

Task tracker communicate with job tracker by sending heartbeat based on which Job tracker decides whether the assigned task is completed or not. If the job tracker does not receive heartbeat from task tracker within specified time, then it will assume that task tracker has crashed and assign that task to another task tracker in the cluster.


Is Namenode machine same as datanode machine as in terms of hardware?

It depends upon the cluster you are trying to create. The Hadoop VM can be there on the same machine or on another machine. For instance, in a single node cluster, there is only one machine, whereas in the development or in a testing environment, Namenode and datanodes are on different machines.


What is a commodity hardware?

Commodity hardware is a non-expensive systems which is not of high quality or high-availability. Hadoop can be installed in any average commodity hardware. We don’t need super computers or high-end hardware to work on Hadoop.


Is Namenode also a commodity?

No. Namenode can never be a commodity hardware because the entire HDFS rely on it. It is the single point of failure in HDFS. Namenode has to be a high-availability machine.


What is a metadata?

Metadata is the information about the data stored in datanodes such as location of the file, size of the file and so on.


What is a daemon?

Daemon is a process or service that runs in background. In general, we use this word in UNIX environment. The equivalent of Daemon in Windows is “services” and in Dos is ” TSR”.


Are Namenode and job tracker on the same host?

No, in practical environment, Namenode is on a separate host and job tracker is on a separate host.


What is a ‘block’ in HDFS?

A ‘block’ is the minimum amount of data of default block size 64MB that can be read or written from or to the HDFS.


If a data Node is full how it’s identified?

When data is stored in datanode, then the metadata of that data will be stored in

the Namenode. So Namenode will identify if the data node is full.


If datanodes increase, then do we need to upgrade Namenode?

While installing the Hadoop system, Namenode is determined based on the size of

the clusters. Most of the time, we do not need to upgrade the Namenode because

it does not store the actual data, but just the metadata, so such a requirement

rarely arise.


On what basis Namenode will decide which datanode to write on?

As the Namenode has the metadata (information) related to all the data nodes, it knows which datanode is free.


Is client the end user in HDFS?

No, Client is an application which runs on your machine, which is used to interact with the Namenode (job tracker) or datanode (task tracker).


What is a rack?

Rack is a storage area with all the datanodes put together. These datanodes can be physically located at different places. Rack is a physical collection of datanodes which are stored at a single location. There can be multiple racks in a single location.


What is Hadoop Single Point Of Failure (SPOF)

If the Namenode fails, the entire Hadoop system goes down. This is called Hadoop Single Point Of Failure.


What is a Secondary Namenode?

The secondary Namenode constantly reads the data from the RAM of the Namenode and writes it into the hard disk or the file system.


Which are the three modes in which Hadoop can be run?

The three modes in which Hadoop can be run are:

1.standalone (local) mode

2.Pseudo-distributed mode

3.Fully distributed mode


What are the features of Stand alone (local) mode?

In stand-alone mode there are no daemons, everything runs on a single JVM. It has no DFS and utilizes the local file system. Stand-alone mode is suitable only for running MapReduce programs during development. It is one of the most least used environments.


What are the features of Pseudo mode?

Pseudo mode is used both for development and in the QA environment. In the

Pseudo mode all the daemons run on the same machine.


Can we call VMs as pseudos?

No, VMs are not pseudos because VM is something different and pesudo is very

specific to Hadoop.


What are the features of Fully Distributed mode?

Fully Distributed mode is used in the production environment, where we have ‘n’

number of machines forming a Hadoop cluster. Hadoop daemons run on a cluster

of machines. There is one host onto which Namenode is running and another host

on which datanode is running and then there are machines on which task tracker

is running. We have separate masters and separate slaves in this distribution.


In which directory Hadoop is installed?

Cloudera and Apache has the same directory structure. Hadoop is installed in

cd/usr/lib/hadoop/


What are the port numbers of Namenode, job tracker and task tracker?

The port number for Namenode is ’50070′, for job tracker is ’50030′ and for task

tracker is ’50060′.


What is the Hadoop-core configuration?

Hadoop core is configured by two xml files:

1.hadoop-default.xml which was renamed to

2.hadoop-site.xml.

These files are written in xml format. We have certain properties in these xml files,

which consist of name and value.


What are the Hadoop configuration files at present?

There are 3 configuration files in Hadoop:

1.core-site.xml

2.hdfs-site.xml

3.mapred-site.xml

These files are located in thehadoop/conf/subdirectory.


How to exit the Vi editor?

To exit the Vi Editor, press ESC and type :q and then press enter.


Which are the three main hdfs-site.xml properties?

The three main hdfs-site.xml properties are:

1.dfs.name.dir which gives you the location on which metadata will be stored and

where DFS is located – on disk or onto the remote.

2.dfs.data.dir which gives you the location where the data is going to be stored.

3.fs.checkpoint.dir which is for secondary Namenode.


What is Cloudera and why it is used?

Cloudera is the distribution of Hadoop. It is a user created on VM by default.

Cloudera belongs to Apache and is used for data processing.


How can I restart Namenode?

1.Click on stop-all.sh and then click on start-all.sh OR

2.Write sudo hdfs (press enter), su-hdfs (press enter), /etc/init.d/ha (press enter)

and then /etc/init.d/hadoop-namenode start (press enter).


What does ‘jps’ command do?

This command checks whether your Namenode, datanode, task tracker, job

tracker, etc are working or not.


How can we check whether Namenode is working or not?

To check whether Namenode is working or not, use the command

/etc/init.d/hadoop-namenode status.


How can we look for the Namenode in the browser?

If you have to look for Namenode in the browser, you don’t have to give

localhost:8021, the port number to look for Namenode in the brower is 50070.


Which files are used by the startup and shutdown commands?

Slaves and Masters are used by the startup and the shutdown commands.


What do slaves consist of?

Slaves consist of a list of hosts, one per line, that host datanode and task tracker

servers.


What do masters consist of?

Masters contain a list of hosts, one per line, that are to host secondary namenode

servers.


What does hadoop-env.sh do?

hadoop-env.sh provides the environment for Hadoop to run. JAVA_HOME is set

over here.


Can we have multiple entries in the master files?

Yes, we can have multiple entries in the Master files.


Where is hadoop-env.sh file present?

hadoop-env.sh file is present in the conf location.


In Hadoop_PID_DIR, what does PID stands for?

PID stands for ‘Process ID’.


What does /var/hadoop/pids do?

It stores the PID.


What does hadoop-metrics.properties file do?

hadoop-metrics.properties is used for ‘Reporting‘ purposes. It controls the reporting

for Hadoop. The default status is ‘not to report‘.


What are the network requirements for Hadoop?

The Hadoop core uses Shell (SSH) to launch the server processes on the slave

nodes. It requires password-less SSH connection between the master and all the

slaves and the secondary machines.


On which port does SSH work?

SSH works on Port No. 22, though it can be configured. 22 is the default Port

number.


Can you tell us more about SSH?

SSH is nothing but a secure shell communication, it is a kind of a protocol that

works on a Port No. 22, and when you do an SSH, what you really require is a

password.


Why password is needed in SSH localhost?

Password is required in SSH for security and in a situation where passwordless

communication is not set.


Do we need to give a password, even if the key is added in SSH?

Yes, password is still required even if the key is added in SSH.


What if a Namenode has no data?

If a Namenode has no data it is not a Namenode. Practically, Namenode will have

some data.


What happens to job tracker when Namenode is down?

When Namenode is down, your cluster is OFF, this is because Namenode is the

single point of failure in HDFS.


What happens to a Namenode, when job tracker is down?

When a job tracker is down, it will not be functional but Namenode will be present.

So, cluster is accessible if Namenode is working, even if the job tracker is not

working.


Can you give us some more details about SSH communication between Masters and the Slaves?

SSH is a password-less secure communication where data packets are sent across

the slave. It has some format into which data is sent across. SSH is not only between

masters and slaves but also between two hosts.


What is formatting of the DFS?

Just like we do for Windows, DFS is formatted for proper structuring. It is not

usually done as it formats the Namenode too.


Does the HDFS client decide the input split or Namenode?

No, the Client does not decide. It is already specified in one of the configurations

through which input split is already configured.


In Cloudera there is already a cluster, but if I want to form a cluster on Ubuntu can we do it?

Yes, you can go ahead with this! There are installation steps for creating a new

cluster. You can uninstall your present cluster and install the new cluster.


Can we create a Hadoop cluster from scratch?

Yes we can do that also once we are familiar with the Hadoop environment.

10 Deadly Interview Questions

If you are like most managers, interviewing is not your favourite task in the world. As a result, many managers avoid the topic. Yet, for something people dislike so much, it is one of the most important tasks a manager must execute. Hiring great people is critical to a company’s success. In a survey, Grant Thornton reviewed 1000 companies in the UK and found companies with the highest growth placed ‘having the best people’ as the most important factor contributing to their company’s growth.

Even more surprising is that in another study, only 8% of corporations in the US have any formal interview training program for hiring managers. When was the last time you had interview training from HR?  Since hiring is a task that comes around infrequently, once or twice every six months for most managers, there is little motivation to invest the time in training.

In absence of formal training the one thing we suggest you can do to improve your interviewing skill is: prepare. Spend 15 minutes before the meeting reviewing the job description, jotting down some questions to ask, and think about what information you need that is not in the resume. Interviewing can be easier than you think but like every successful meeting, it all starts with a well orchestrated plan. And if nothing else, please at least read the resume before the interview.

Still need some help? Here are some interview questions that may give some inspiration to step up your interview game.

1. Tell me why I should not hire you.

Probably one of the toughest question to ask and slightly unfair.  Answers are ripe with pit holes and can really throw a candidate off.  This question is designed to test their ability to think on their feet. The best answers are ones that take an apparent negative and make it positive.  Recommended not to start your interview with this question.

2. Rate yourself on a scale of one to ten.

Yikes, who wants to answer this one? If you give yourself a 6, then you are showing a lack of self confidence and you may not be hired. On the other hand, if you think you’re a 10, you may be labelled as unmanageable and miserably egotistical. The safest response is middle ground, between 8 and 9. This says they are confident, capable, and hard-working, but they know there is always room for improvement.

3. Everyone takes home the occasional pen from the supply room. What is the most expensive thing you’ve taken?

This is a great question to challenge someone’s moral compass. What makes this a tough question is that it implies everyone steals from their employers and that it is okay to do so. A person must be confident enough to challenge the first statement. Since the interview is usually stressful many people will let their guard and reveal the craziest things. Make sure you preface the question with the question with the initial statement; otherwise you are just accusing some of stealing.

4. Tell me about your greatest error in judgment.

A nice question to determine if your candidate is a model employee or if they have the ability to do the job correctly. The story they choose to tell in response should be unrelated to their previous jobs and should have occurred sometime in the distant past. Also they must be able to talk how they have grown and learned from this mistake. Choosing something recent and/or work related may highlight weaknesses and indicate incompetence.

5. What did you tell your boss to get the time off to come to this interview?

Great question to start the interview. It may seem like an icebreaker question, but they are establishing they integrity. They either declare themselves a liar or said they had a doctor’s appointment. The only answer to this question is they are there on their own time, either using a vacation day or part of their lunch hour.

6. Your Manager gives you a large important project to complete by end of day and the President of the company asks you to clean up the office for an important client coming in. What do you do?

This question is less about the answer given and more about a person’s ability to make a decision they can justify.  It also gives insight to prioritization. The natural response for most people is to do as the president asks. The candidate will ask themselves ‘what answer does this person want to hear?’ It becomes a dilemma for the candidate. Asking more questions to better learn about the scenario is a good sign.

7. Tell me about a situation in which you would be willing to take a pay cut.

Another killer question. Are they a team player, would they take one for the team, or are they here only for the money? This question can lead to many responses, but use it to drill down to learn about their money motivations.

8. What is more important: money or time off?

A simple question, but one that will without fail stump many candidates. If they answer the question with money, it will seem greedy and that they will leave at the first job offer that pays higher. If they choose time off, then they may feel that they would be perceived as a slacker. This is a trap question.

9. Have you ever been fired from a job?

Direct question few people are willing to ask directly. Use it sparingly. If the answer yes, do not jump to any conclusions; investigate more. There may be a good reason.

10.  Tell me about the job you hated the most

Using this question is only effective if the interviewer spends some time understanding why and exploring what the person was doing. Dig deep on the specifics of the job duties. Do not take a one or two sentence answer.

Storage Interview Questions

SAN


What is storage array?

What is storage virtualization?

What are the main constrains of SCSI in storage networking?

What advantages would using an iSCSI Storage Area Network (SAN) give to your organization over using Direct Attached Storage (DAS) or a Fibre Channel SAN?

What is the smallest unit of information transfer in FC?

What is Multipath I/O?s

What is zoning?

What are the main constrains of SCSI in storage networking?

What are different types of protocols used in transportation and session layers of SAN?

What are the types of disk array used in SAN?

What are the protocols used in physical/datalink and network layer of SAN?

How storage virtualization helps to create SAN?


What is storage virtualization?


What is storage array?

How do you install device drivers for the HBA first time during OS installation?

What are application software available to manage Storage Area Network?

What are minimum components needed to establish Basic Storage Area Network?

What is Network Attached Storage (NAS)?

What is difference between SAN and NAS? How SAN is better than NAS?



Fiberchannel


List the comparison between FC and FCOE?

Explain FC login process?

How many classes of service are available in Fibre Channel?

What are the services provided by Fabric to all the nodes?

What are the layers of Fibre Channel Protocol?

What is the smallest unit of information transfer in FC?

What is Simple name server (SNS)?

How does FC Switch maintain the addresses?

What are the 5 states of Arbitrary Loop in FC?

What is zoning?

What are the layers of Fibre Channel Protocol?

What is the difference between LUN and WWN?

What are the services provided by Fabric to all the nodes?

How many classes of service are available in Fibre Channel?

What is the type of Encoding used in Fibre Channel?

What are different types of protocols used in transportation and session layers of SAN?

What are the protocols used in physical/datalink and network layer of SAN?

which are the FC SAN topologies?

When you will deploy Fibre Channel SAN instead of iSCSI SAN?

What are Link speed currently available for Fibre Channel SAN? What is Future?

FCOE



List the comparison between FC and FCOE?

What are benefits of iSCSI SAN over FCOE SAN?

What are the layers of FCOE Protocol?

What are different types of protocols used in transportation and session layers of SAN?

What are the protocols used in physical/datalink and network layer of SAN?

What are benefits of iSCSI SAN over FCOE SAN?

what are Link Speed available for FCOE SAN?

What is future of FC SAN vs FCOE SAN

What is applications of FCOE?

Compare between FCOE and iSCSI

What is FCOE?

Things to Remember in OSPF

DR and BDR

DR - Designated Router and BDR backup designated Router are Routers on a Broadcast segment. For example Ethernet a DR and optionally an BDR is chosen. The election is based on

• The highest priority on the interface
  • Default priority is 1. Can be set in the range 0 - 255
  • If priority is set to 0 the router can not be a DR
  • The priority is set on a per-link basis.
• The highest RID - Router ID

interface fastethernet 0/0
 ip ospf priority 255

RID: Router ID

The RID is the IP address which the Router is known as.

1. Set manually
2. Highest Loopback IP address
3. Highest IP address if no Loopbacks defined

interface Loopback 0
 ip address 10.10.10.1
!
interface Loopback 1
 ip address 192.168.10.1
!
router ospf 1
  router-id 10.10.10.1

Stub Areas

OSPF RFC's describe Stub and Not-So-Stubby-Area. Totally Stub Area is a Cisco proprietary standard.

What is Stub Areas

Stub Areas are part of a network which don't need to have a copy of the total Link-State database. It reduces the memory requirements and CPU overhead of the router. Often stub areas only have a default gateway.

Stub Area

• Stub Areas blocks Type 5 LSA's. (External Routes)
  • Routing to the outside world is based on a default route.
  • A Stub Area will accept Summary Routes from other Areas.

Totally Stub Area

• totally Stub Areas blocks Type 3,4 and 5 LSA's. Only a default gateway.
  • Has a default route out of the Area,

NSSA: Not So Stubby Area

• A NSSA imports a limited number of External Routes. The number of Routes is limited to those Routes required to provide connectivity between Areas.

Example

Example

Stub Area example

Example

Totally Stub Area example

Example

NSSA: Not So Stubby Areas

Example

Example

Example

Example

Virtual links

Example

Example

Example

Single Area configuration

Example 1

Example network 1

hostname R1 ! interface fastethernet 0/0 ip address 192.168.0.1 255.255.255.0 ! interface fastethernet 0/1 ip address 10.0.1.1 255.255.255.0 ! router ospf 88 network 192.168.0.0 0.0.0.255 area 0 network 10.0.1.0 0.0.0.255 area 0	hostname R2 ! interface fastethernet 0/0 ip address 192.168.0.2 255.255.255.0 ! interface fastethernet 0/1 ip address 10.0.2.1 255.255.255.0 ! router ospf 77 network 192.168.0.0 0.0.0.255 area 0 network 10.0.2.0 0.0.0.255 area 0
hostname R3 ! interface fastethernet 0/0 ip address 192.168.0.3 255.255.255.0 ! interface fastethernet 0/1 ip address 10.0.3.1 255.255.255.0 ! interface serial 0/0 ip address 172.16.0.1 255.255.255.252 ! router ospf 66 network 192.168.0.0 0.0.0.255 area 0 network 10.0.3.0 0.0.0.255 area 0 network 172.16.0.0 0.0.0.3 area 0	hostname R4 ! interface fastethernet 0/1 ip address 10.0.4.1 255.255.255.0 ! interface serial 0/0 ip address 172.16.0.2 255.255.255.252 router ospf 66 network 172.16.0.0 0.0.0.3 area 0 network 10.0.4.0 0.0.0.255 area 0

Default administrative Distance

 

Cisco implementation

Default Administrative Distance (metric)

Route Source	Distance
Connected Interface	0
Static Route out an Interface	0
Static Route to a next hop	1
EIGRP summary route	5
External BGP	20
Internal EIGRP	90
IGRP	100
OSPF	110
IS-IS	115
RIP (Version 1 og 2)	120
EGP	140
ODR (On Denmand Routing)	160
External EIGRP	170
Internal BGP	200
Ukendt source	255

 

LSA Types

 

LSA Types

Type	ABR	Sent to	Meaning
1	O	224.0.0.5	Router Link: Indeholder alle Routerens Links. Floodes til Area
2	O	224.0.0.6	Network Link: Floodes fra DR til Area. Indeholder alle Naboer på MA-medie
3	O IA		Summary Link: Sendes fra Area til Area gennem ABR. Indeholder IA Summaries.
4	O IA		ASBR summary Link: Sendes fra ASBR’s. Indeholder externe router.
5	O E1/2		Externe Router fra ASBR. E1 intern + extern cost. E2 kun extern cost.
7	O E1/2		Externe Routes fra ASBR i NSSA
8			OSPF and BGP internetworking
9,10,11			Opaque LSA used by Cisco for MPLS

 

The following are descriptions of each type of LSA.

 

Type 1

Every router generates router link advertisements for each area to which it belongs. A type 1 LSA describes the collective states of the directly connected links (interfaces) of the router. These LSAs are flooded only within the area in which they are originated.

 

  Type 2

A type 2 LSA is generated for every transit broadcast and NBMA network within an area. A transit network has at least two directly attached OSPF routers. Ethernet is an example of a transit network.
The DR of the network is responsible for advertising the network LSA. A type 2 network LSA lists each of the attached routers that make up the transit network, including the DR itself, as well as the subnet mask used on the link. The type 2 LSA then floods to all routers within the transit network area. Type 2 LSAs never cross an area boundary. The link-state ID for a network LSA is the IP interface address of the DR that advertises it.

Type 3

The ABR sends type 3 summary LSAs. Type 3 LSAs advertise any networks owned by an area to the rest of the areas in the OSPF autonomous system, as shown in Figure .
The link-state ID is set to the network number; the mask is also advertised.

By default, OSPF does not automatically summarize groups of contiguous subnets or summarize a network to its classful boundary. The network operator uses configuration commands to specify how the summarization occurs. By default, a type 3 LSA is advertised into the backbone area for every subnet defined in the originating area, which can cause significant flooding problems. Consequently, you should always consider using manual route summarization at the ABR.

Summary LSAs are flooded throughout a single area only, but are regenerated by ABRs to flood into other areas.

Note By default, summary LSAs do not contain summarized routes.

Type 4

A type 4 summary LSA is generated by an ABR only when an ASBR exists within an area. A type 4 LSA identifies the ASBR and provides a route to it. The link-state ID is set to the ASBR router ID. All traffic destined to an external autonomous system requires routing table knowledge of the ASBR that originated the external routes.

In Figure , the ASBR sends a type 1 router LSA with an external bit (e bit) that is set to identify itself as an ASBR. When the ABR, which is identified with a border bit (b bit) in the router LSA, receives the type 1 LSA, it builds a type 4 LSA and floods it to the backbone (area 0). Subsequent ABRs regenerate a type 4 LSA to flood into their areas.

Type 5

Type 5 external LSAs describe routes to networks outside the OSPF autonomous system. Type 5 LSAs are originated by the ASBR and are flooded to the entire autonomous system.

The link-state ID is the external network number. Because of the flooding scope, and depending on the number of external networks, the default lack of route summarization can be a major issue with external LSAs. Therefore, you should summarize blocks of external network numbers at the ASBR to reduce flooding problems.

Type 6

Type 6 LSAs are specialized LSAs that are used in multicast OSPF applications.

Type 7

Type 7 is an LSA type that is used in not-so-stubby areas (NSSAs). They are originated by ASBRs within NSSAs and are flooded only within the NSSA in which they originated.

Type 8

Type 8 is a specialized LSA that is used in internetworking OSPF and Border Gateway Protocol (BGP).

Types 9, 10, and 11

The opaque LSAs, types 9, 10, and 11, are designated for future upgrades to OSPF for application-specific purposes. For example, Cisco Systems uses opaque LSAs for Multiprotocol Label Switching (MPLS) with OSPF. Opaque LSAs are distributed using standard LSDB flooding mechanisms. Each type has a different flooding scope.

Notes

• loopback interfaces advitces as /32 unless ip ospf network point-to-point command is run on the Interface. 

 

Vmware Interview Questions - Part 3

Click here for Part 1

Click here for Part 2

What is the maximum Hosts in Linked‐mode environment?

• 1000

What is the maximum Hosts per datacenter?

• 100

What is the maximum Hosts per vCenter Server if the vCenter Server is running on a 64-Bit OS ?
• 300

What is the maximum Hosts per vCenter Server if the vCenter Server is running on a 32-Bit OS ?

• 200

What is the maximum Linked vCenter Server systems?

• 10


What is the Maximum Floppy controllers per virtual machine?

• 1

What is the Maximum VMDirectPath SCSI targets per virtual machine?

• 60

What is the Maximum Virtual SCSI adapters per virtual machine?

• 4

What is the Maximum Virtual SCSI targets per virtual SCSI adapter?

• 15

What is the Maximum IDE controllers per virtual machine?

• 1

What is the Maximum Parallel ports per virtual machine?

• 3

What is the Maximum Floppy devices per virtual machine?

• 2

What is the Maximum Virtual SCSI targets per virtual machine?

• 60

What is the Maximum VMDirectPath PCI/PCIe devices per virtual machine?

• 2

What is the Maximum RAM per virtual machine?

• 255GB

What is the Maximum Virtual machine swap file size?

• 255GB

What is the Maximum IDE devices per virtual machine?

• 4

What is the Maximum Virtual CPUs per virtual machine (Virtual SMP) ?

• 8

What is the Maximum Concurrent remote console connections to a virtual machine?

• 40

What is the Maximum Virtual NICs per virtual machine?

• 10

What is the Maximum Serial ports per virtual machine?

• 4

What is the Maximum virtual machine Disk Size?

• 2TB minus 512B

Vmware Interview Questions - Part 2

Click Here for Part 1


1. Explain the physical topology of Virtual Infrastructure 3 Data Centre?

a typical VMware Infrastructure data center consists of basic physical building blocks such as x86 computing servers, storage networks and arrays, IP networks, a management server and desktop clients.

2. How do you configure Clusters, Hosts, and Resource Pools in VI3?

A cluster is a group of servers working together closely as a single server, to provide high availability, load balancing and high performance.  A host is a single x86 computing server with individual computing and memory resources. Resource pools are allocation of the available resources in to pieces for the proper distribution.

3. What are resource pools & what’s the advantage of implementing them?

A VMware ESX Resource pool is a pool of CPU and memory resources. Inside the pool, resources are allocated based on the CPU and memory shares that are defined. This pool can have associated access control and permissions. Clear management of resources to the virtual machines.

4. Explain why VMware ESX Server is preferred over Virtual Server or Workstation for enterprise implementation?

For better resource management as it has a virtualization layer involved in its kernel, which communicates with the hardware directly.

5. In what different scenarios or methods can you manage a VI3 ?

Using the Virtual Infrastructure Client we can manage one esx server, using virtual center we can manage more than 1 esx server.. and also we can use service console to manage it.
http://searchvmware.techtarget.com/tip/0,289483,sid179_gci1280576_mem1,00.html

6. Explain the difference between access through Virtual Infrastructure Client (vi client), Web access, Service Console access(ssh) ?

Using VI Client we can access the ESX server as well as Virtual Center Server also, here we can use unix type of authentication or windows type authentication. But to access the service console, we should use unix type of authentication preferably even though we can access the service console through ad authentication using esxcfg-auth, but it does not support all functions to work on, all the functions are available only with root account which is based on red hat Linux kernel. Using the web access also we can manage virtual center as well as a single host. But all the enterprise features are not supported.

Console access to the Service Console

The disadvantages to this mode are

you must be at the console (or connect using an IP KVM) and
you must know Linux to accomplish your task (no GUI).

SSH to the Service Console

You can SSH to the console prompt of an ESX server and receive the same Linux text console access as I showed above. Telnet is not allowed. To use this method, the ESX server must be working on the network and you must have an SSH client on your PC to connect. Again, in this mode, you don't get a GUI interface.

VMware Virtual Infrastructure (VI) Web Access to the ESX Server

This is the VMware VI Web Access interface. The benefit to using this is that you get a GUI client for your ESX server without having to install a client on your local machine. The downside to the web interface is that you can only perform basic ESX functions like controlling existing machines (start/stop/pause) and console remote access. You cannot add new VMs, work with VM storage, or VM networks. Still, this is a great interface if you just need to check the status of your ESX VMs, restart a VM, or use console remote control.

VMware Virtual Infrastructure Client (VI Client) to the Server

The benefits to the VI client are that you have full access to do whatever is needed on the ESX Server and you get a GUI client to do it in. The only downside is that you must install the VI client application to do this. However, the installation is negligible and the VI client is the absolute best way to administer your ESX Server.

VMware Virtual Infrastructure Client (VI Client) to the Virtual Center Server (VC Server)

From this VI VC interface, you can manage all ESX servers, VM storage, VM networks, and more. Virtual Center, of course, is an optional product that requires additional licenses and hardware.

7. Explain advantages or features of VMware Virtual Machine File System (VMFS) ?

It’s a clustered file system, excellent support for sharing between ESX servers in a cluster.

Features

Allows access by multiple ESX Servers at the same time by implementing per-file locking. SCSI Reservations are only implemented when LUN meta data is updated (e.g. file name change, file size change, etc.)

Add or delete an ESX Server from a VMware VMFS volume without disrupting other ESX Server hosts.
LVM allows for adaptive block sizing and addressing for growing files allows you to increase a VMFS volume on the fly (by spanning multiple VMFS volumes)
With ESX/ESXi4 VMFS volumes also can be expanded using LUN expansion
Optimize your virtual machine I/O with adjustable volume, disk, file and block sizes.
Recover virtual machines faster and more reliably in the event of server failure with Distributed journaling.

Limitations

Can be shared with up to 32 ESX Servers.
Can support LUNs with max size of 2TB and a max VMFS size of 64 TB as of version 4 (vSphere).
"There is a VMFS-3 limitation where each tree of linked clones can only be run on 8 ESX servers. For instance, if there is a tree of disks off the same base disk with 40 leaf nodes in the tree, all 40 leaf nodes can be simultaneously run but they can only run on up to 8 ESX hosts."
VMFS-3 limits files to 262,144 (218) blocks, which translates to 256 GB for 1 MB block sizes (the default) up to 2 TB for 8 MB block sizes.

8. What are the types of data stores supported in ESX3.5 ?

iSCSI datastores, FC SAN datastores, Local VMFS, NAS and NFS

9. How can you configure these different types of datastores on ESX3.5 ?

If we have FC cards installed on the esx servers, by going to the storage option, we can scan for the luns.

10.What is Vmware Consolidate Backup (VCB) ? Explain your work exposure in this area ?
VMware Consolidated Backup is  a backup framework, which enables 3rd party tools to take backups. VCB is used to help you backup your VMware ESX virtual servers. Essentially, VCB is a "backup proxy server". It is not backup software. If you use VCB, you still need backup software. It is commonly installed on its own dedicated Windows physical server.

Here are the benefits of VMware's VCB:

 •Centralize backups of VMware ESX Virtual Servers
 •Provide file-level backups of VMware ESX Virtual Servers - both full and incremental (file level backup available to only Windows guests)
 •Provide image-level backups
 •Prevent you from having to load a backup agent on every Virtual Machine
 •Prevent you from having to shutdown Virtual Machines to get a backup
 •Provides LAN-Free backup because the VCB server is connected to the SAN through your fibre channel adaptor
 •Provides centralized storage of Virtual Server backups on the VCB server, that is then moved to your backup tapes through the 3rd party backup agent you install
 •Reduces the load on the VMware ESX servers by not having to load a 3rd party backup agent on either the VMware ESX service console or on each virtual machine.
 •Utilizes VMware Snapshots

Basically, here is how VCB works:

 •If you are doing a file level backup, VCB does a snapshot of the VM, mounts the snapshot, and allows you to backup that mounted "drive" through VCB to your 3rd party backup software
 •If you are doing an image level backup of the VM, VCB does a snapshot of the VM, copies the snapshot to the VCB server, unsnaps the VM, and allows you to backup the copied snapshot image with your 3rd party backup software.


11. How do you configure VMware Virtual Centre Management Server for HA & DRS ? What are the conditions to be satisfied for this setup?

HA & DRS are the properties of a Cluster. A Cluster can be created only when more than one host added, in that case we need to configure HA & DRS as well to provide High Availability and Load balancing between hosts and for the virtual machines.

12.Explain your work related to below terms :
VM Provisioning:  Virtual Machine  Creation.
Alarms & Event Management: Alarms are used to know the status of the resource usage for a VM. Events are used monitor the tasks that are taken place on the esx servers or in the virtual center
Task Scheduler: Task scheduler, if you want to schedule a task it will be used, for example if you want move one vm from one host to another host or if you want shutdown/reboot a vm etc.
Hardware Compatibility List: what are the hardware that compatible with ESX OS.

13.What SAN or NAS boxes have you configured VMware with ? How did you do that ?

Storage team will provide the LUN information, with that we will add those LUNs to ESX hosts from VM storage.

14.What kind of applications or setups you have on you Virtual Machines ?

Exchange server and Share Point, but these are for DEMO purposes, Cirtrix presentation servers etc.

15. Have you ever faced ESX server crashing and Virtual Centre Server crash? How do you know the cause of these crashes in these cases ?

16. Will HA work if Virtual Center Server is down ?

A1) HA continues to work if VC is down - the agents are initially configured by virtual center, but HA operations are controlled by local agents on ESX. VC does NOT monitor the ESX servers for HA. ESX servers monitor each other.
DRS do not work while VC is down.
A2) For DRS, the config and logic is completely in VC.
For HA, only the config is in VC. The logic is in the service consoles, and that's where the reaction is coming from. VC will notice the HA reaction afterwards when it connects to the service consoles the next time.
No, Why because all these futures are comes with Virtual Center only.

17. What are the situations which triggers vMotion automatically?

Resource Contention between virtual machines (DRS)
Distributed power management

18. What is DRS/HA/DPM/dvSwitch/FT/vApps/vSafe/vShields ? :-)

DRS : Distributed Resource Scheduling
HA : High Availability
DPM : Distributed Power Management
dvSwitch : Distribute vSwitch – It’s a new feature introduced in vSphere4.0
FT : Fault Tolerance for Virtual Machines – it’s a new feature introduced in vSphere4.0
vApps : vApp is a container same as resource pool, but it is having some features of virtual machines, a vApp can be powered on or powered off, and it can be cloned too.
http://communities.vmware.com/message/1308457#1308457

vmSafe : VMsafe's application programming interfaces are designed to help third-party vendors create virtualization security products that better secure VMware ESX, vShield Zones is a security tool targets the VMware administrator.

vShield : VShield Zones is essentially a virtual firewall designed to protect VMs and analyze virtual network traffic. This three-part series describes vShield Zones, explains how to install it and provides useful management tips. To begin, let's get started with the basics: what vShield Zones is and how it works.

http://searchvmware.techtarget.com/tip/0,289483,sid179_gci1363051_mem1,00.html

19. What are the requirement for FT ?
http://communities.vmware.com/thread/209955

20. What are the differences between ESX and ESXi ?

ESX is an OS with full features of virtualization, ESXi is a limited features OS with 32MB image.

21. Which are the new features introduced in vSphere 4 ? *****

1. 64-bit hypervisor - Although not everyone realized it, the hypervisor in ESX Server 3.5 was 32-bit. As a result, ESX Server 3.5 couldn't take full advantage of today's more powerful 64-bit hardware platforms. ESX Server 4.0 uses a native 64-bit hypervisor that provides significant performance and scalability enhancements over the previous versions. However, the new hypervisor does require a 64-bit hardware platform.

2. Increased VM scalability - ESX Server 4.0's new 64-bit architecture provides significant increases in scalability. ESX Server 4.0 supports virtual machines (VMs) with up to 255GB of RAM per VM. In addition, the vSphere 4.0 Enterprise Plus edition provides support for up to 8-way virtual SMP per VM. The other editions support up to 4-way virtual SMP. These gains are available on both Windows and Linux guests.

3. Hot add CPU, RAM, and virtual disks - This important enhancement in vSphere 4.0 is designed to create a dynamic IT infrastructure through the ability to add CPU, RAM, and virtual disks to a running VM. The hot add capability lets you dynamically increase your VMs' performance during periods of high resource demands.

4. Thin provisioning - This feature is nothing new to Microsoft virtualization users; vSphere now offers a thin-provisioning feature that's essentially the equivalent of Hyper-V's dynamic disks. Thin provisioning lets you create and provision a Virtual Hard Disk (VHD), but the host uses only the amount of storage that's actually required by the VM rather than using the VHD's allocated size.

5. VMware Fault Tolerance - Fault Tolerance is a new high-availability feature in vSphere 4.0. Fault Tolerance works only between two systems. It uses a technology called vLockstep to provide protection from system failure with absolutely no downtime. VMware's vLockstep technology keeps the RAM and the virtual processors of two VMs in sync at the instruction level.

6. vNetwork Distributed Switch—vSphere 4.0's vNetwork Distributed Switch lets you create and share network configurations between multiple servers. The vNetwork Distributed Switch spans multiple ESX Server hosts, letting you configure and manage virtual networks at the cluster level. It also lets you move network configuration and state with a VM when the VM is live migrated between ESX Server hosts.

7. IPv6 support - Another enhancement in vSphere 4.0 is support for IPv6. Many organizations are planning to move to IPv6. vSphere's IPv6 support lets customers manage vCenter Server and ESX Server hosts in mixed IPv4/IPv6 network environments.

8. vApps—vApps essentially lets you manage as a single entity multiple servers that comprise an n-tiered application. Using vApps, you can combine multiple VMs, their interdependencies, and their resource allocations together as a unit. You can manage all the components of the vApps as a single unit, letting you power off, clone, and deploy all the vApps components in the same operations.

9. vSphere Host Update Utility—The new vSphere Host Update Utility lets you centrally update your ESXi and ESX Server 3.0 and later hosts to ESX Server 4.0. The UI displays the status of the remote updates in real time.

10. VMware vShield Zones—VMware's new vShield Zones let customers enforce network access protection between VMs running in the virtual data center. The vShield Zones feature lets you isolate, bridge, and firewall traffic across vCenter deployments.

22. Which are the traffic shaping options available to configure?23. What is promiscuous mode ?

If the promiscuous mode is enabled for a switch, the traffic sent that switch will be visible to all vm’s connected to that switch. I mean, the data will be broadcasted.

24. What makes iSCSI and FC diffrent ?
Addressing Scheme, iSCSI relies on IP and FC not, and the type of transfer of data also. In FC the data transferred as blocks, in iSCSI the data transferred as files. The cabling also, FC uses Fibre cable and iSCSI uses RJ45.
25. What is the format for iSCSI addressing ?

IP Address

26. VM's Task Manager shows performance normal, But vCenter reports high resource utilization, what is the reason ?
Search KEY WORDS : VM's performance normal,  vCenter reports high resource utilization
http://communities.vmware.com/message/897975

27. What are the different types of memory management tricks available under ESX ?

http://en.wordpress.com/tag/esx-memory-management/

http://www.cs.northwestern.edu/~fabianb/classes/cs-443-s05/ESX.pps

28. What is vmmemctl ?

http://pubs.vmware.com/vi3/resmgmt/wwhelp/wwhimpl/common/html/wwhelp.htm?context=resmgmt&file=vc_advanced_mgmt.11.24.html

29. How we can list pNICs & status using command line ?

ifconfig –a

30. What is resource pool ? What are the use of it ?
A resource pool is a logical abstraction for flexible management of resources. Resource pools can be grouped into hierarchies and used to hierarchically partition available CPU and memory resources.

31. How HA works.
VMware HA provides high availability for virtual machines by pooling them and the hosts they reside on into a cluster. Hosts in the cluster are monitored and in the event of a failure, the virtual machines on a failed host are restarted on alternate hosts.

32. Is HA dependent on virtual center
(Only for Install)
33. What is the Maximum Host Failure allowed in a cluster
(4)
34. How does HA know to restart a VM from a dropped Host
(storage lock will be removed from the metadata)

35.How many iSCSI targets will ESX support
8 for 3.01, (64 for 3.5)
36 How Many Fiber Channel targets
(256) (128 on Install)

37 What is Vmotion

(ability to move running vm from one host to another)

38 What is virtual SMP –
when and why should you give a vm multiple vCPUs - part of their answer whould be that best pracrtice is to start with a single vCPU because of you can run into perfomance issues do to CPU scheduling

39 Ask what version of Linux kernel does ESX run

if they are truly experienced they should say ESX is not Linux and does not use a Linux kernel - and give them an extra poijnt if they explain that the service console runs a modified version of Red Hat Ent 3 -

40 does HA use vmotion?

the answer is no - vm stops and restarts on ESX other host

41. what is the different when you use viclient connect to VC and directly to ESX server itself.

When you connect to VC you manage ESX server via vpxa (Agent on esx server). Vpxa then pass those request to hostd (management service on esx server). When you connect to ESX server directly, you connect to hostd (bypass vpxa). You can extend this to a trobleshoot case, where connect to esx see one thing and connect to VC see another. So the problem is most likely out of sync between hostd and vpxa, "service vmware-vpxa restart" should take care of it.

42. What was the most difficult VMWare related problem/issue you faced in a production environment and what were the specific steps you took to resolve it?

HA issues – because of dns problems, the hosts are unable to communicate together. Corrected by adding all servers ip’s in each server’s /etc/hosts file
VM was not powered up –because the swap file was locked by another host, when I try to power on the vm its not powering up. After releasing the lock its powered on.

43. When was the last time you called VM Support and what was the issue?

Licensing related issues.

44. What was the most performance intensive production app that you supported in VMware and what were the some of the challenges that it posed?

In exchange sharepoint demo project, getting lot of VLAN issues. (its my experience, you can say yours)

45. How would you determine that a perf intensive app is a good candidate? Spefically what tools would you use to identify candidates. Specifically inside those tools what metrics would you use?

46. What is yor philosophy on how much of the data center can be virtualized? (If the interviewer wants max virtualization, but the interviewee is not convinced that this is a good idea, this could be a deal breaker)

47. What is your opinion on the virtualization vendors (MS vs VM vs Citrix vs etc) and why? (Just trying to figure out if the candidate is keeping up with this ever changing virtualization market)

48. I beleive another good question would be to ask the candidate to briefly describe VST, VGT & EST mode and 802.1Q trunking. I say this because networking is such an important part of VMware implementations and on going support.., do you really want a VMware engineer working in your environment if they lack the knowledge of these concepts (+unless of course they are only delegated with low level permissions for generic VM operations+)

More information on these mode's can be found here: www.vmware.com/pdf/esx3_vlan_wp.pdf
Also ask the candidate to explain why one mode would be used as opposed to another?, remember that there can be numerous reasons for the use of different modes depending on your company/client's network, security policies etc..

49. If you are interviewing for a consultant role it would also be a good scenario to provide a brief overview of a fictional network and ask the candidate to do a whiteboard draft of how the network would be layed out if say the ESX servers have 6 NIC's or 8 NIC's etc.. etc...

50. What are notable files that represent a VM?

.vmx – configuration settings for VM
.vmxf – configuration settings used to support an XML-based VM configuration API
.vmtx – configuration settings for a Template VM (replaces the .vmx file)
.vmdk – virtual disk file. (Note: if a thick disk is used, a–flat.vmdk file that represents the actual monolithic disk file will exist but will be hidden from the vSphere Client.)
.nvram – non-volatile memory (BIOS)
.vswp – swap file used by ESX/ESXi per VM to overcommit memory, i.e. use more memory than physically available. This is created by the host automatically when powering on a VM and deleted (default behavior) when powering off a VM. Swap files can remain and take up space if a host failed prior to shutting down a VM properly. Normally the swap file is stored in the location where the VM configuration files are kept; however the location can be optionally located elsewhere—for example, locally for performance reasons and if using NAS/NFS, local swap should be used.
.vmss – suspend file (if placed into suspend power mode)
.vmsd – for snapshot management
.vmsn – snapshot file

51. Host Profiles
What licensing is required for Host Profiles? Available with vSphere Enterprise Plus edition.

52 Can Host Profiles work with ESX/ESXi 3.x hosts?
•No. Only starting with ESX/ESXi 4.0.

53 Can Host Profiles be used with a cluster running both ESX and ESXi hosts?
•Yes, but remember to use an ESX host and not an ESXi host to create a profile for use.
•In theory, Host Profiles should work with mixed host clusters, as it translates ESX to ESXi, but be careful as there are enough differences between ESX and ESXi that can lead you to make self-inflicted errors when applying Host Profiles. The easiest method is to create clusters that are homogeneous and maintain two different profiles for these two types of clusters.

54 Can Host Profiles work when using the Cisco Nexus 1000v?
•No, because Host Profiles was designed with the generic vNetwork Distributed Switch. The Cisco Nexus 1000v switch gives administrators finer-grained control of the networking beyond what Host Profiles can apply.

55. What are host profiles?
A set of best practiced configuration rules, which are can be applied to entire cluster or to an individual host. So that all the hosts in sync with each other, this will avoid vmotion, drs and ha problems.
56. Could not power on VM: no swap file
My ESXi 3.5 machine runs 8-10 VMs (Win2k3 and WinXP) normally. At the moment, 5 of them are complaining that they cannot Power On. They seem to start and then complain "Could not power on VM: no swap file". I had a look with the data browser. It's a small installation, so the vswp files ought to be in the same directory as the vmx file (I did not inttionally put them anywhere else). Of course I don't see a vswp file there because the machine is not running. I don't know enough about the vmx file structure to identify if anything is wrong in the specifications. I have downloaded one of the vmx files and attached it here. Please either tell me what to change in that vmx file, or suggest another approach to get the machines to start.
57. What are the available Storage options for virtual machines ? Raw device mappings, VMFS
inShare0
There are two ways to provision storage for virtual machines (VMs) on a storage area network (SAN). One way is to use VMFS, the proprietary, high-performance clustered file system provided with VMware Infrastructure (VI). Using virtual disks (VMDK files) on VMFS is the preferred option for most enterprise applications, and as such supports the full range of functionality available in a VI implementation, including VM snapshots, VMotion, Storage VMotion, and VMware Consolidated Backup (VCB).
The other way to provision storage is Raw Device Mapping (RDM). RDMs are sometimes needed in instances where virtualized access to the underlying storage would interfere in the operation of software running within the VM. One such example is SAN management software, which typically requires direct access to the underlying hardware; and thus would need to use an RDM instead of a virtual disk. In this tip, I'll discuss what RDMs are and when to use them over a virtual disk.
Defining raw device mappings
An RDM is a file that resides within a VMFS volume that acts as a proxy, or an intermediary, for a raw physical device. One can think of an RDM as a symbolic link to a raw LUN. The RDM contains metadata and other information about the raw physical device being accessed and can, depending upon the configuration of the RDM, add features like VMotion support and snapshots to VMs that are using raw LUNs.
Why use RDMs instead of virtual disk

58. What are the differences between Virtual and Physical compatibility modes when mapping the Raw Devices to virtual machines?

You can configure RDM in two ways:
Virtual compatibility mode—this mode fully virtualizes the mapped device, which appears to the guest operating system as a virtual disk file on a VMFS volume. Virtual mode provides such benefits of VMFS as advanced file locking for data protection and use of snapshots.

Physical compatibility mode—this mode provides access to most hardware characteristics of the mapped device. VMkernel passes all SCSI commands to the device, with one exception, thereby exposing all the physical characteristics of the underlying hardware. In this mode, the mapping is done as follows, when we create a mapping, the configuration stored in a file and that file is stored with the vm files in datastore. This file points to the raw device and makes it accessible to the vm.

59. What are RDM Limitations?

RDM limitations
There are two types of RDMs: virtual compatibility mode RDMs and physical compatibility mode RDMs. Physical mode RDMs, in particular, have some fairly significant limitations:
•No VMware snapshots
•No VCB support, because VCB requires VMware snapshots
•No cloning VMs that use physical mode RDMs
•No converting VMs that use physical mode RDMs into templates
•No migrating VMs with physical mode RDMs if the migration involves copying the disk
•No VMotion with physical mode RDMs

Virtual mode RDMs address some of these issues, allowing raw LUNs to be treated very much like virtual disks and enabling functionality like VMotion, snapshotting, and cloning. Virtual mode RDMs are acceptable in most cases where RDMs are required. For example, virtual mode RDMs can be used in virtual-to-virtual cluster across physical hosts. Note that physical-to-virtual clusters across boxes, though, require physical mode RDMs.

While virtual disks will work for the large majority of applications and workloads in a VI environment, the use of RDMs--either virtual mode RDMs or physical mode RDMs--can help eliminate potential compatibility issues or allow applications to run virtualized without any loss of functionality.

Vmware Interview Questions - Part 1

1. VMWare Kernel is a Proprietary Kenral and is not based on any of the UNIX operating systems, it's a kernel developed by VMWare Company.

2. The VMKernel can't boot it by itself, so that it takes the help of the 3rd party operating system. In VMWare case the kernel is booted by RedHat Linux operating system which is known as service console.

3. The service console is developed based up on Redhat Linux Operating system, it is used to manage the VMKernel

4. To restart webaccess service on vmware
service vmware-webaccess restart – this will restart apache tomcat app

5. To restart ssh service on vmware
service sshd restart

 

6. To restart host agent(vmware-hostd) on vmware esx server
service mgmt-vmware restart

7. Path for the struts-config.xml
/usr/lib/vmware/webAccess/tomcat/apache-tomcat-5.5.17/webapps/ui/WEB-INF/

8. To start the scripted install the command is
esx ks=nfs:111.222.333.444:/data/KS.config ksdevice=eth0
location device name

9. Virtual Network in Simple……………….

Virtual Nic(s) on Virtual Machine(s) ----->

Physical Nic on the ESX Server (Virtual Switch - 56 Ports) ----->

Physical Switch Port Should be trunked with all the VLANS to which the VM's need access

All the ESX servers should be configured with Same number of Physical Nics (vSwitches) and Connectivity also should be same, So that vMotion succeeds
All the Virtual Machines are connected to one vSwitch with Different VLANS, this means the Physical Nic(vSwitch) needs to be trunked with the same VLANS on the Physical Switch Port

10 What are the three port groups present in ESX server networking
1. Virtual Machine Port Group - Used for Virtual Machine Network
2. Service Console Port Group - Used for Service Console Communications
3. VMKernel Port Group - Used for VMotion, iSCSI, NFS Communications

11. What is the use of a Port Group?
The port group segregates the type of communication.

 

12. What are the type of communications which requires an IP address for sure ?
Service Console and VMKernel (VMotion and iSCSI), these communications does not happen without an ip address (Whether it is a single or dedicated)

13. In the ESX Server licensing features VMotion License is showing as Not used, why?
Even though the license box is selected, it shows as "License Not Used" until, you enable the VMotion option for specific vSwitch

14. How the Virtual Machineort group communication works ?

All the vm's which are configured in VM Port Group are able to connect to the physical machines on the network. So this port group enables communication between vSwitch and Physical Switch to connect vm's to Physical Machine's

15. What is a VLAN ?
A VLAN is a logical configuration on the switch port to segment the IP Traffic. For this to happen, the port must be trunked with the correct VLAN ID.

 

16. Does the vSwitches support VLAN Tagging? Why?
Yes, The vSwitches support VLAN Tagging, otherwise if the virtual machines in an esx host are connected to different VLANS, we need to install a separate physical nic (vSwitch) for every VLAN. That is the reason vmware included the VLANtagging for vSwitches. So every vSwitch supports upto 1016 ports, and BTW they can support 1016 VLANS if needed, but an ESX server doesn’t support that many VM’s. :)

17. What is Promiscuous Mode on vSwitch ? What happens if it sets to Accept?
If the promiscuous mode set to Accept, all the communication is visible to all the virtual machines, in other words all the packets are sent to all the ports on vSwitch
If the promiscuous mode set to Reject, the packets are sent to inteded port, so that the intended virtual machine was able to see the communication.

 

18. What is MAC address Changes ? What happens if it is set to Accept ?
When we create a virtual machine the configuration wizard generates a MAC address for that machine, you can see it in the .vmx (VM Config) file. If it doesn't matches with the MAC address in the OS this setting does not allow incoming traffic to the VM. So by setting Reject Option both MAC addresses will be remains same, and the incoming traffic will be allowed to the VM.

19. What is Forged Transmits ? What happens if it is set to Accept ?
When we create a virtual machine the configuration wizard generates a MAC address for that machine, you can see it in the .vmx (VM Config) file. If it doesn't matches with the MAC address in the OS this setting does not allow outgoing traffic from the VM. So by setting Reject Option both MAC addresses will be remains same, and the outgoing traffic will be allowed from the VM.

 

20. What are the core services of VC ?
VM provisioning , Task Scheduling and Event Logging

21. Can we do vMotion between two datacenters ? If possible how it will be?
Yes we can do vMotion between two datacenters, but the mandatory requirement is the VM should be powered off.

22. What is VC agent? and what service it is corresponded to? What are the minimum req's for VC agent installation ?
VC agent is an agent installed on ESX server which enables communication between VC and ESX server.
The daemon associated with it is called vmware-hostd , and the service which corresponds to it is called as mgmt-vmware, in the event of VC agent failure just restart the service by typing the following command at the service console

" service mgmt-vmware restart "
VC agent installed on the ESX server when we add it to the VC, so at the time of installtion if you are getting an error like " VC Agent service failed to install ", check the /Opt size whether it is sufficient or not.

23. How can you edit VI Client Settings and VC Server Settings ?
Click Edit Menu on VC and Select Client Settings to change VI settings
Click Administration Menu on VC and Select VC Management Server Configuration to Change VC Settings

24. What are the files that make a Virtual Machine ?
.vmx - Virtual Machine Configuration File
.nvram - Virtual Machine BIOS
.vmdk - Virtual Machine Disk file
.vswp - Virtual Machine Swap File
.vmsd - Virtual MAchine Snapshot Database
.vmsn - Virtual Machine Snapshot file
.vmss - Virtual Machine Suspended State file
.vmware.log - Current Log File
.vmware-#.log - Old Log file

25. What are the devices that can be added while the virtual Machine running
In VI 3.5 we can add Hard Disk and NIC's while the machine running.

In vSphere 4.0 we can add Memory and Processor along with HDD and NIC's while the machine running

 

 

26. How to set the time delay for BIOS screen for a Virtual Machine?
Right Click on VM, select edit settings, choose options tab and select boot option, set the delay how much you want.

27. What is a template ?
We can convert a VM into Template, and it cannot be powered on once its changed to template. This is used to quick provisioning of VM's.

 

23. What to do to customize the windows virtual machine clone,?
copy the sysprep files to Virtual center directory on the server, so that the wizard will take the advantage of it.

24. What to do to customize the linux/unix virtual machine clone,?
VC itself includes the customization tools, as these operating systems are available as open source.

25. Does cloning from template happens between two datacenters ?
Yes.. it can, if the template in one datacenter, we can deploy the vm from that template in another datacenter without any problem.

26. What are the common issues with snapshots? What stops from taking a snapshot and how to fix it ?
If you configure the VM with Mapped LUN's, then the snapshot failed. If it is mapped as virtual then we can take a snapshot of it.
If you configure the VM with Mapped LUN's as physical, you need to remove it to take a snapshot.

27. What are the settings that are taken into to consideration when we initiate a snapshot ?
Virtual Machine Configuration (What hardware is attached to it)
State of the Virtual Machine Hard Disk file ( To revert back if needed)
State of the Virtual Machine Memory (if it is powered on)

 

28. What are the requirements for Converting a Physical machine to VM ?
An agent needs to be installed on the Physical machine
VI client needs to be installed with Converter Plug-in
A server to import/export virtual machines

29. What is VMWare consolidated backup ?
It is a backup framework, that supports 3rd party utilities to take backups of ESX servers and Virtual Machines. Its not a backup service.

30. To open the guided consolidation tool, what are the user requirements ?
The user must be member of administrator, The user should have "Logon as service" privileges - To give a user these privileges,open local sec policy, select Logon as service policy and add the user the user should have read access to AD to send queries

 

 

How VMWare Kernel different from other kernels?

VMWare kernel is a proprietary kernel that means that it is a registered kernel by VMWare Company and it is not based on any other kernel architecture or any other operating system. VMWare consists of a kernel that requires an operating system to boot it. A service console is being provided when VMWare kernel is booted.

What are the features provided by VMWare for easy access?

VMWare provides several features to make it easy for the user to access and maintain it. The features are as follows:
• VMWare provides web browser interface
• It provides easy to use wizard to configure the settings
• It provides tools to easily create hosts and maintain it from one place
• It provides easy maintenance of Virtual machines
• It provides easy graphics to configure the VMWare settings for security

What are the features of VMWare Player?

VMWare player is a stand-alone player that comes with the installation of VMWare also. The features that make it more popular are as follows:

• Creation of virtual machines can be done with easy install options. The creation and installation can be done directly to the system.
• VMWare Player can run any virtual machine and it can be used by anyone, anywhere. It allows quick and easy access, to take the advantage of security, portability and flexibility to manage the virtual machines.
• VMWare player allows sharing of virtual machines with other computers or users.

What are the different components used in VMWare infrastructure?

The different and major components used in VMWare infrastructure is as follows:
1. VMWare infrastructure consists of the lowest layer which acts as a ESX server host.
2. VMWare infrastructure also use the virtual centre server that keep tracks of all the VM related images and manage it from one point.
3. VMWare infrastructure (VI) client: this allows the client to interact with user's applications that are running on VMWare.
4. Web browser is used to access the virtual machines.
5. License server is used to create a server that provides licensing to the applications
6. Database servers are used to maintain a database.

What are the benefits of virtualization?

Virtualization is a creation of virtual machines and to manage them from one place. It allows the resources to be shared with large number of network resources. Virtualization is having lots of benefits and they are as follows:
1. It helps in saving lots of cost and allows to easily maintaining it, in less cost.
2. It allows multiple operating systems on one virtualization platform.
3. It removes the dependency of heavy hardware to run the application.
4. It provides consolidating servers that are used for crashing of a server purpose
5. It reduces the amount of space being taken by data centres and company data.

What is the purpose of a Hypervisor?

Hypervisor is a program that manages the virtual machine. It also act like virtual machine manager that manages the many virtual machines from one place. It allows multiple operating system to share single hardware host. Each operating system in this consists of its own defined space consisting of space, memory and processor. It is used as a controller program to control host processors and resources. It separates out the layer between many operating systems so that one can't conflict with another one.

How ESX server related to VMWare?

ESX server is the enterprise edition of VMWare. It provides server virtualization platform that allows many operating systems to be shared together in a convenient way and consists of a centralized management platform that is also known as virtual centre. ESX server is a virtualization technique that is used to create cloud applications and allows easy development of cloud platforms. It is related to VMWare as it is the upper layer of it.
              

What is the difference between ESX and GSX server?

GSX server acts as type 2 hypervisor that gets installed on the host operating system’s hardware like windows and Linux. VMWare workstation gets mixed up with GSX server to provide it more functionality to run your applications and operating systems. ESX server on the other hand, is type 1 hypervisor that runs its software directly on the system’s hardware and it doesn’t require any operating system prior to its installation. It is level 0 hypervisor and it has its own operating system.

What is the use of VMWare workstation?

VMWare workstation is software that allows user to run more than one operating system in there system. It provides virtualization to run different applications on many operating systems at a single time. It saves the current configuration of operating system for the user in the form of virtual machines. VMWare allows user to view there application and work with so many different OS without even switching between the OSs.

What are the different types of extensions used by VMWare?

1. .log: is used to keep a log file to maintain a key for VMWare. This file allows user to see the problems encountered during any installation or while using VMWare.
2. .nvram: is used to store the state of the virtual machine in system’s BIOS.
3. .vmdk: is a virtual disk file that is used to store the content of virtual machine.
4. .vmsd: stores the information and metadata of the system’s snapshots.
5. .vmsn: is used to store the snapshot state. It stores both the running state and the time when you have taken it.
6. .vmss: stores the suspended state of a virtual machine.
7. .vmtm: stores the configuration team data.
8. .vmx: store the primary configurations for the new virtual machine.

How virtual machine’s concept is different for host and guest systems?

Host system is the system that runs the operating system and over which the virtual platform can be installed. The virtual platform that runs another operating system is called as guest operating system. Host and guest can be connected with each other by using the virtual machines. A host system that runs all together its own operating system is called as virtualization host and the guest operating system will be that, which get installed over that operating system.

What are some major differences between VMWare Server and ESX server?

• ESX server is a bare metter virtualation platform that is a physical server whereas, VMWare server needs an operating system to run itself.
• ESX server is type 1 hypervisor virtualization platform whereas, VMWare server is a type-2 hypervisor virtualization platform.
• ESX server gives better performance then VMWare server, due to less overhead.
• ESX server have more features available then VMWare server.
• VMWare server is good to be used on small platforms and with less resources but, ESX server requires high specifications.

What is the use of Para-virtualization? Para-virtualization is a virtualization technique that allows similar virtual machines to be created on particular hardware. It allows many operating systems to run on host hardware at the same time. It makes good use of resources like processors, memory and networking. It acts as a virtual machine monitor that has high performance and more efficient. It is used for development, testing and production of the virtual machines. It also good in disaster recovery by moving the guest virtual machine till the hardware is being repaired. Why snapshots are really important in VMWare? Snapshots are images that is been taken at a particular point from the virtual guest operating system. The snapshot consists of the virtual machine configurations, memory and the devices that were present at the time of the snapshot. By doing this, you can return back to virtual machine which might have become corrupted or might not be working. Snapshots can be taken anytime according to your need and requirement. Snapshots can be saved and then system can be reverted back in case of any disaster happened to your operating system. What are the disadvantages associated with VMWare virtualization platform? The disadvantage of VMWare virtualization platform is as follows: • VMWare concept requires the knowledge of the concept. • It requires money to buy the resources required for virtualization platform. • It requires high end server with lots of high end configuration and specification that increases the cost. • It requires different technologies that have to be implemented for the enterprise virtualization systems. • Reliability decreases and cost increases in case of the system failures.