Tuesday, February 4, 2014

FAIQ-Frequently Asked Interview Questions- VMware Related

As I was preparing for Job Change..I started brushing up on my vmware skills and simultaneously helping the community. Here i'm sharing some of the questions that are Frequently being asked in interviews..i will update these questions with appropriate answers and VMware KB articles..

1. Linked Mode Considerations for vCenter Server?
Ans.
Ensure that each vCenter Server instance in a Linked Mode group is part of a domain and not a workgroup. Each instance can be in a different domain if the domains have a two-way trust relationship 
between themselves 

  • DNS must be operational in order for Linked Mode replication to work 
  • DNS name of the vCenter Server system must match the actual machine name 
  • Ensure that vCenter Server system is not a domain controller 
  • Ensure that vCenter Server system is not a terminal server 
  • Ensure that the installer is run by a domain user who is an administrator of the vCenter Server machine and the target machine of the Linked Mode group 
  • Ensure that the domain user account has the following permissions: 
  • o Member of the Administrators group 
  • o Act as part of the operating system 
  • o Log on as a service 
  • Ensure that the vCenter Server instances are running network time synchronization and their time is not more than 5 minutes apart 
  • Ensure that the Network Service account has permissions to write to the vCenter Server installation folder

2. Pre-requisites for Site Recovery Manager (SRM)?
Ans.

 SRM System Requirements
Processor

 2.0GHz or higher Intel or AMD x86 processor

 Memory

 2GB minimum

 Disk Storage

 5GB minimum

 Networking

 1 Gigabit recommended for communication between SRM sites.

3. Different Admission control policies and how you will calculate slots?  
Ans.
Amount of host failures

Percentage reserved

Designated failover host

 Slot size-HA uses the highest CPU reservation of any given VM and the highest memory reservation of any given VM. For ex, If VM1 has 2GHZ and 1024MB reserved and VM2 has 1GHZ and 2048MB reserved the slot size for memory will be 2048MB+memory overhead and the slot size for CPU will be 2GHZ.

4. Explain Link aggregation protocol used in Distributed switch (vDS)? 
5. Background process of a P2V operation?
Ans.
P2V involves the process of decoupling and migrating a physical server's operating system (OS), applications, and data from that physical server to a virtual-machine guest hosted on a virtualized platform.

6. Architectural difference between the HA of ESXi 4.0 and 5.0?
Ans.
ESXi 4.1 and prior uses an agent called “AAM” aka Legato Automated Availability Management. 
With ESXi 5.0 comes a new HA architecture. HA has been rewritten from the ground up to shed some of those constraints that were enforced by AAM. HA as part of 5.0, also referred to as FDM (fault domain manager), introduces less complexity and higher resiliency. From a UI perspective not a lot has changed, but there is a lot under the covers that has changed though, no more primary/secondary node concept as stated but a master/slave concept with an automated election process.
Extra Points- http://www.yellow-bricks.com/vmware-high-availability-deepdiv/#HA-50

7. How to upgrade ESX 3.5 to ESXi 5.0?
Ans.
Not supported for direct upgrade.
You must upgrade version 3.x ESX and ESXi hosts to ESX or ESXi version 4.x before you can upgrade them to ESXi 5.0. See the vSphere 4.x upgrade documentation.

Alternatively, you might find it simpler and more cost effective to do a fresh installation of ESXi 5.0.

8. How Windows licensing works in the VMware environment?
Ans. 
License for each Edition
Standard     per VM   10 VM means 10 license
Enterprise  per VM    10 VM means 3 License(1 enterprise license for 4 VMs)
Datacenter per socket  2 socket means 2 license.Unlimited VM per box
Extra Points-http://microsoftlicensereview.com/tag/microsoft-licensing-with-vmware/

9. After the manual vmotion of a two VMs from one esx host to another esx host in a cluster, I am not able to ping one VM, but i am able to ping the second VM?what is the reason behind this.....
Ans. The no of ports on the virtual switch got exhausted.

10. After the Vmotion of a VM, how does the physical switch knows that the VM is migrated to another esx host and now switch must  send packets to the new esx host's virtual switch on which VM is currently residing?
Ans. its the virtual switch who does the reverse ARP not the esx host

11. What is difference between Storage/Array based replication and host based replication in VMware SRM. which one to use , when and why?
Ans.
SRM supports array‐based replication in which one or more storage arrays at the protected site replicate their data to peer arrays at the recovery site. Storage replication adapters (SRAs) are array‐specific programs that array vendors provide to support the use of array‐based replication by SRM. SRAs are not part of an SRM release. Your array vendor provides and supports SRAs.

 Host Based Replication or HBR for short. this is an accurate description and it was the feature name during the beta phase.  However, by the time SRM 5.0 went to GA, each of the replication components went through a name change vSphere Replication.
Extra Points-http://www.boche.net/blog/index.php/2011/10/03/srm-5-0-replication-bits-and-bytes/

12. How election process between many esxi host occurs in one cluster(Vsphere 4, 5 and Vsphere 5.1)
Ans.
vSphere 5.1- Election process is almost similar to vSphere 5.0.
vSphere 5.0-A master is elected by a set of HA agents whenever the agents are not in network contact with a master. A master election thus occurs when HA is first enabled on a cluster and when the host on
which the master is running:

  1.  fails,
  2.  becomes network partitioned or isolated,
  3.  is disconnected from vCenter Server,
  4.  is put into maintenance or standby mode,
  5.  or when HA is reconfigured on the host.

The HA master election takes approximately 15 seconds and is conducted using UDP. While HA won’t
react to failures during the election, once a master is elected, failures detected before and during the
election will be handled. The election process is simple but robust. The host that is participating in the
election with the greatest number of connected datastores will be elected master. If two or more hosts
have the same number of datastores connected, the one with the highest Managed Object Id will be
chosen. This however is done lexically; meaning that 99 beats 100 as 9 is larger than 1. For each host,
the HA State of the host will be shown on the Summary tab. 

 vSphere 4.1-It is a common misconception that a re-election occurs when a primary node fails. This is not the case. The promotion of a secondary host only occurs when a primary host is either put in “Maintenance Mode”, disconnected from the cluster, removed from the cluster or when you do a reconfigure for HA.If all primary hosts fail simultaneously no HA initiated restart of the VMs will take place. HA needs at least one primary host to restart VMs. This is why you can only take four host failures in account when configuring the “host failures” HA admission control policy.

13. How to do P2V using Vmware Converter and what are the ports requirement for P2V?
14. How to migrate(P2V) a SQL server without any downtime using vmware converter?
Ans.
For P2V of a SQL server, my practice has been to convert the system drive (C:\) of the source system and utilize one of two recovery strategies. The first is to create the data volume of the SQL server on the destination virtual machine initially empty, then restore a SQL backup onto the new, empty system. While you can convert the SQL database server's data volumes with the SQL Server service stopped, it is usually cleaner to have an absolutely consistent database on the virtual machine. This can be done by restoring from a SQL backup or an agent-based backup if you are using a tool that does this type of protection.

 Extra Points-http://virtualizationreview.com/blogs/everyday-virtualization/2010/03/~/media/ECG/vrt/100316vr_van01.ashx
15. List of check performed before and after P2V process?
16. List of issues faced at the time of P2V?
17. What is Distributed switch (vDS)?
Ans.
Functions as a single switch that spans across all associated hosts.  This allows virtual machines to maintain consistency in regards to their network connection as the vMotion and move from host to host.  dvSwitches have mostly the same characteristics of a Standard switch in the way that they can connect VMs to VMs as well as VMs to external networks.  dvSwitches require Enterprise Plus licensing, and allow you to above and beyond some capabilities of the standard switch with options to use netflow, port mirroring and private VLANs.

18. Difference between Distributed switch (vDS) and Cisco Nexus 1000v switch and standard switch (vSS)?
Ans.

19. If the vCenter server is down, will Distributed switch (vDS) work?
Ans.
Yes, VM communication will work with external world.

20. What is the requirements for installing vCenter?
21. How much minimum RAM and space need for vCenter Installation?
Ans.

22. Role of VPXA client and working?
Ans.
The VirtualCenter Agent, also referred to as vpxa or the vmware-vpxa service, is what allows a VirtualCenter Server to connect to a ESX host. Specifically, vpxa is the communication conduit to the hostd, which in turn communicates to the ESX kernel.

 Extra Points- Troubleshooting the vCenter Server Agent when it does not start (1006128)

23. Difference between ESX and ESXi?
Ans.

24. Difference between ESX3.5, ESX4 and ESXi 5?
25. Licensing in vSphere 5 and different types of licenses and their difference?
Ans.
26. Different method to upgrade ESX server?
27. What is host profile?
Ans.
Host Profiles helps us to  maintains consistent configuration across the datacenter by using Host Profiles policies and also eliminates Manual host configuration/ Host Profile Policies captures the blue print of well known configured  ESX host in environment and it also acts a reference host to configure other hosts in environment.  These policies capture the blueprint of a known, validated reference host configuration which is also called as "Golden Image". The blue print contains the information about the networking, storage, security and other settings.

28. What is FT, requirement and how to configure FT and how FT works?
Ans.
FT provides a higher level of protection by making VMs continuously available in the event of a HOST FAILURE (FT will not protect if the OS blue screens or an application fails on the primary VM, the secondary VM will do the same).  FT keeps the states of a primary and secondary VM identical by using VMware vLockstep technology.  The vLockstep technology replays all instructions from the primary VM on the secondary.  If the host running the primary VM fails, the secondary becomes the new primary, and a new secondary is created.  This will occur even if vCenter is not available.

FT Requirements

Cluster Requirements

  • Host Certificate checking must be enabled
  • At least 2 FT-certified hosts running the same FT version or host build number.
  • Hosts need access to the same storage
  • FT Logging and VMotion Networking need to be configured.
  • HA must be enabled on the cluster.  If it isn't you will not be able to power on an FT machine or add a host running an FT machine already to the cluster.

Host Requirements

  • Must contain processors from the FT-compatible processor group.  Highly recommended that CPUs are also compatible with one another.
  • Must be licensed for FT (Enterprise or Enterprise Plus)
  • Must be certified for FT (HCL).
  • BIOS must have Hardware Virtualization (HV) enabled.

VM Requirements

  • Virtual disks must either be in virtual RDM mode or VMDK files (no physical RDM). The disk must also be in thick format.
  • VM files must be stored on shared storage (FC, FCOE, iSCSI, NFS, NAS).
  • Cannot have more than one cpu.
  • Must be running on Windows 7, Windows Server 2008, Vista, 2003, XP, 2000, NT 4, All Linux supported by ESX, Netware, solaris 10, and FreeBSD ( there are some limitations on processors though, so check them out).


29. How to increase the size of Hard disk in win 2008 and win 2003?
30. What is Hot CPU / Add RAM?
Ans.
VMware vSphere's hot-add RAM and hot-plug CPU functions allow you to add additional virtual hardware to running virtual machines. The benefit of being able to do this is the ability to provide more resources to your machines without bringing servers down to add the additional resources. Simply put, this is additional capacity without downtime.
31. How hot CPU/RAM works of 2008 and 2003 whether we need a reboot for applying hot CPU/add RAM?
Ans.
32. What is PSA?
Ans.
To manage storage multipathing, ESX/ESXi uses a special VMkernel layer, Pluggable Storage Architecture (PSA). The PSA is an open modular framework that coordinates the simultaneous operation of multiple multipathing plugins (MPPs). PSA is a collection of VMkernel APIs that allow third party hardware vendors to insert code directly into the ESX storage I/O path. This allows 3rd party software developers to design their own load balancing techniques and failover mechanisms for particular storage array. The PSA coordinates the operation of the NMP and any additional 3rd party MPP.

33. What is VAAI?
Ans.
vStorage APIs for Array Integration is a feature introduced in ESXi/ESX 4.1 that provides hardware acceleration functionality. It enables your host to offload specific virtual machine and storage management operations to compliant storage hardware. With the storage hardware assistance, your host performs these operations faster and consumes less CPU, memory, and storage fabric bandwidth.
Extra Points-Frequently Asked Questions for vStorage APIs for Array Integration (1021976)

34. SCSI reservation?
Ans.
ESX uses a mechanism of "locking" called "scsi reservation" to share luns between ESX hosts. These "reservations" are non-persistent and are released when they require activity is completed. The Service Console regularly monitors the luns and checks for an "reservations" that have aged to old. The ESX host will then try releasing the lock. If however another application running from the Service Console is using the lun, it can immediately reclaim the "lun" or place another "reservation". Thus, if 3rd party applications are not design to release their locks, we see a continuous flood of heartbeat reclaiming events in the logs.SCSI reservations are needed to prevent any data corruption in environment where LUNs are shared between many hosts.Every time a host tries to update the VMFS metadata it needs to put SCSI reservation on it.

35. SCSI reservation has been removed in vSphere 5?
Ans.
Yes/No, The Atomic Test and Set (ATS) primitive is used for locking on Virtual Machine File System (VMFS) datastores for VMware vSphere Storage APIs for Array Integration (VAAI) compatible storage arrays. It is far superior to the SCSI Reservation locking technique.

36. How data integrity is achieved in vSphere 5?
Ans.
Integrity checks verify and maintain data integrity on the deduplication store. The output of an integrity check 
is a checkpoint. By default, VDP creates an integrity check every day during the maintenance window. In 

addition, you can start the integrity check manually.

37. HA difference between vSphere 4 and vSphere 5?
Ans.
With vSphere 5.0 comes a new HA architecture. HA has been rewritten from the ground up to shed some of those constraints that were enforced by AAM. HA as part of 5.0, also referred to as FDM (fault domain manager), introduces less complexity and higher resiliency.no more primary/secondary node concept as stated but a master/slave concept with an automated election process.the complete agent as been rewritten and the dependency on VPXA has been removed. HA talks directly to hostd instead of using a translator to talk to VPXA with vSphere 4.1 and prior. FDM agent also communicates with vCenter and vCenter with the FDM agent. As of vSphere 5.0, HA leverages vCenter to retrieve information about the status of virtual machines and vCenter is used to display the protection status of virtual machines. On top of that, vCenter is responsible for the protection and unprotection of virtual machines. This not only applies to user initiated power-offs or power-ons of virtual machines, but also in the case where an ESXi host is disconnected from vCenter at which point vCenter will request the master HA agent to unprotect the affected virtual machines. two minor chances but huge improvements when it comes to managing/troubleshooting HA which I want to point out:
  • No dependency on DNS
  • Syslog functionality
vSphere 4.1 and prior uses an agent called “AAM” aka Legato Automated Availability Management. A VMware HA Cluster consists of nodes, primary and secondary nodes. Primary nodes hold cluster settings and all “node states” which are synchronized between primaries. Node states hold for instance resource usage information. In case that vCenter is not available the primary nodes will have a rough estimate of the resource occupation and can take this into account when a fail-over needs to occur. Secondary nodes send their state info to the primary nodes. Nodes send a heartbeat to each other, which is the mechanism to detect possible outages. Primary nodes send heartbeats to primary nodes and secondary nodes. Secondary nodes send their heartbeats to primary nodes only. Nodes send out these heartbeats every second by default. The first 5 hosts that join the VMware HA cluster are automatically selected as primary nodes.  All the others are automatically selected as secondary nodes. When you do a reconfigure for HA the primary nodes and secondary nodes are selected again, this is at random.
Extra Points-http://www.yellow-bricks.com/vmware-high-availability-deepdiv/

38. What is RDM and How many types of RDM exists?
Ans.
RDM is a mapping file in a separate VMFS volume that acts as a proxy for a raw physical storage device. The RDM allows a virtual machine to directly access and use the storage device. The RDM contains metadata for managing and redirecting disk access to the physical device.
The file gives you some of the advantages of direct access to a physical device while keeping some advantages of a virtual disk in VMFS. As a result, it merges VMFS manageability with raw device access.

RDMs can be described in terms such as mapping a raw device into a datastore, mapping a system LUN, or mapping a disk file to a physical disk volume. All these terms refer to RDMs.
Two compatibility modes are available for RDMs:

  • Virtual compatibility mode allows an RDM to act exactly like a virtual disk file, including the use of snapshots.
  • Physical compatibility mode allows direct access of the SCSI device for those applications that need lower level control.


39. Why we use VLAN ID 4095?
Ans.
This particular VLAN ID is only to be used for “Virtual Guest Tagging” (VGT). It basically means that the VLAN ID is stripped off at the Guest OS layer and not at the portgroup layer. In other words the VLAN trunk(multiple VLANs on a single wire) is extended to the virtual machine and the virtual machine will need to deal with it.

There aren’t many use cases any more. In the past it was used to increase the number of VLANs for a VM. The limit of 4 NICs for VI3 meant a maximum of 4 portgroups / VLANs per VM. However with vSphere the maximum amount of NICs went up to 10 and as such the amount of VLANs for a single VM also went up to 10.

40. What is VGT?
Ans. VLAN configuration on virtual switches, physical switches, and virtual machines (1003806)
Virtual Guest Tagging (VGT)

  • All VLAN tagging is performed by the virtual machine.
  • You must install an 802.1Q VLAN trunking driver inside the virtual machine.
  • VLAN tags are preserved between the virtual machine networking stack and external switch when frames are passed to/from virtual switches.
  • Physical switch ports are set to trunk port.
41. vMotion does not check vSwitch port availability? True or False?

 42. How storage DRS works?
Ans.
VMware DRS aggregates computing capacity across a collection of servers into logical resource pools and intelligently allocates available resources among the virtual machines based on pre-defined rules that reflect business needs and changing priorities.VMware DRS allows users to define the rules and policies that decide how virtual machines share resources and how these resources are prioritized among multiple virtual machines.When a virtual machine experiences increased load, VMware DRS first evaluates its priority against the established resource allocation rules and policies, and if justified, allocates additional resources. Resources are allocated to the virtual machine by either migrating it to another server with more available resources or by making more “space” for it on the same server by migrating other virtual machines to different servers. The live migration of virtual machines to different physical servers is executed completely transparent to end-users through VMware VMotion.VMware DRS can be configured to operate in either automatic or manual mode. In automatic mode, VMware DRS determines the best possible distribution of virtual machines among different physical servers and automatically migrates virtual machines to the most appropriate physical servers. In manual mode, VMware DRS provides a recommendation for optimal placement of virtual machines, and leaves it to the system administrator to decide whether to make the change.

43. Different types of load balancing policy at the vSwitch?
Ans.
In a vSwitch, load balancing policies describe the different techniques that will be used for distributing the network traffic from all the virtual machines that are connected to the vSwitch and its subordinate Port Groups across the physical NICs associated with the vSwitch. There are several options available for load balancing as shown below:

  1. Load Balancing Policies
  2. vSwitch Port Based (default)
  3. MAC Address Based
  4. IP Hash Based
  5. Explicit Failover Order


Extra Points-http://kensvirtualreality.wordpress.com/2009/04/05/the-great-vswitch-debate%E2%80%93part-3/

44. What is beacon probing?
Ans.
Beacon Probing – this sends a probe down the line and can detect upstream failures past the initial port is connected to.  Useful in situations where there is no physical connection to the first switch down the line such as configurations like hp c-class blades.

45. Different security policies at the vSwitch?
Ans.
vSS and vDS Security Policies include
  • Promiscuous Mode (Reject by Default) – Allows a VM to see all traffic flowing through the switch, even that which is not destined for that VM.
  • MAC Address Changes (Accept by Default) – Can block or allow traffic destined to a VM which has had it's effective MAC Address changed.  May need to change the effective MAC address on a VM in order to support Microsoft NLB.
  • Forged Transmits (Accept by Default)  - Essentially the same as MAC Address Changes except dealing with traffic being transmitted by the VM.
46. If we don't have VMware tool on VM, can we take snapshot? Explain?
Ans.
Without VMware tools install we can take snaptshot. but snapshot with quiesce the virtual machine files, verify that the virtual machine is powered on and that VMware Tools is installed.

47. What happened in the background if we commit the snapshot?
48. How many log files get created in VM folder and what would be there sequence?
Ans.

49. Once you take snapshot, How much MB delta file get created in?
Ans.

50. What is Change Block Tracking (CBT)?
Ans.
Changed Block Tracking (CBT) is a VMware feature that helps perform incremental backups. VMware Data Recovery uses this technology and so can developers of backup and recovery software.

 Virtual machines running on ESX/ESXi hosts can track disk sectors that have changed. This feature is called Changed Block Tracking (CBT). On many file systems, CBT identifies the disk sectors altered between two change set IDs. On VMFS partitions, CBT can also identify all the disk sectors that are in use.
Virtual disk block changes are tracked from outside virtual machines, in the virtualization layer. When software performs a backup, it can request transmission of only the blocks that changed since the last backup, or the blocks in use. The CBT feature can be accessed by third-party applications as part of the vSphere APIs for Data Protection (VADP). Applications call VADP to request that the VMkernel return blocks of data that have changed on a virtual disk since the last backup snapshot.

51. How you will troubleshoot different types of snapshot problems?
Ans.


52. How vMotion works?
Ans.
There are 3 underlying action happening in vMotion.
1)The entire state of a virtual machine is encapsulated by a set of files stored on shared storage such as Fibre Channel or iSCSI Storage Area Network (SAN) or Network Attached,Storage (NAS).VMware vStorage VMFS allows multiple ESX to access the same virtual machine files concurrently.

 2)The active memory and precise execution state of the virtual machine is rapidly transferred over a high speed network, allowing the virtual machine to instantaneously switch from running on the source ESX host to the destination ESX host.VMotion keeps the transfer period imperceptible to users by keeping track of on-going memory transactions in a bitmap.Once the entire memory and system state has been copied over to the target ESX host, VMotion suspends the source virtual machine, copies the bitmap to the target ESX host, and resumes the virtual machine on the target ESX host.This entire process takes less than two seconds on a Gigabit Ethernet network.

 3)The networks being used by the virtual machine are also virtualized by the underlying ESX host, ensuring that even after the migration, the virtual machine network identity and network connections are preserved. VMotion manages the virtual MAC address as part of the process. Once the destination machine is activated, VMotion pings the network router to ensure that it is aware of the new physical location of the virtual MAC address.

53. What is Jumbo Frames and its requirements?
Ans.
Jumbo Frames allow a host to send larger frames (up to 9k) out on the network, but must be configured all throughout the network.  Jumbo Frames is enabled on the vSS and vDS by simply setting the Max MTU to 9000 on the port groups.
Inside the VM you must install the VMXNET 3 adapter and enabled Jumbo Frames from within the OS itself.

 54. Link aggregation and its requirements?
55. Snapshot implementation has been changed in vsphere 5. What are the changes?
56. Snapshot files are visible in snapshot manager but they are visible in console.  How you will delete these snapshot files?
57. How you will troubleshoot locked file issues?
Ans. 
A running virtual machine creates lock files to prevent consistency problems on virtual disks. If the virtual machine did not use locks, multiple virtual machines might read and write to the disk, causing data corruption.
Lock files are always created in the same directory as the .vmdk files.
Investigating hosted virtual machine lock files (1003857)
Investigating virtual machine file locks on ESXi/ESX (10051)

58. One user is complaining that his server is working very slow. How you will troubleshoot this issue?
59. What is storage I/O control (SIOC)?
Ans.
Storage I/O Control is a method that VMware can manage and prioritize I/O for virtual machines. These VMs are typically contained within a vSphere cluster and use a shared datastore. It performs this function by using similar concepts of shares and limits that you would be familiar with from CPU and memory that has been around in vSphere for years. VMware can then dynamically allocate I/O across the nodes in a vSphere cluster. You will need to own the Enterprise Plus licensing level to take advantage of SIOC.

 Extra Points-how SIOC calculates latency across all hosts

60. What is network I/O control (NIOC)?
Ans.
Network resource pools determine the bandwidth that different network traffic types are given on a vSphere distributed switch.When network I/O control is enabled, distributed switch traffic is divided into the following predefined network resource pools: Fault Tolerance traffic, iSCSI traffic, vMotion traffic, management traffic, vSphere Replication (VR) traffic, NFS traffic, and virtual machine traffic.

 Extra Points-NIOC Old and New Architecture

61. One user is not able to take the RDP of a vCenter but the vCenter is pinging. How will you resolve the issue?
Ans.
After verifying the procedures in the environment overview and establishing connectivity to the customers network via vpn, rdp, or another remote support app try the following:

 Ping the vcenter server to verify it is online, after a successful ping test try to use the vSphere Client to connect to the Virtual Center server. If this succeeds use the GUI client to check to see if there are errors or alarms triggered. Normally there are yellow or red icons to indicate this.
If you can ping the vcenter server but cannot connect to it with the vSphere Client try using RDP to login to the server. Sometimes there are problems with SQL server not starting quickly enough which causes the Virtual Center Server service to not start. If this is the case go into the MS Windows Services control panel and try to manually start the VMware Virtual Center Server service.
VIM_CMD notes

 vim_cmd vmsvc/power.off

 vim_cmd vmsvc/power.shutdown

 vim_cmd vmsvc/getallvms

 When a virtual machine appears as “Invalid”, but you can still RDP to the server…
Log into the host esx/esxi server and remove the VM from inventory, then browse the datastore and readd it back to inventory and everything should be ok.

62. The server is showing black screen in vSphere client. How will you analyze the issue?
63. What are affinity and anti affinity rules and what are other rule apart from these two rules in vSphere 5?
Ans.
You can control the placement of virtual machines on hosts within a cluster by using affinity rules.
You can create two types of rules.
■
Used to specify affinity or anti-affinity between a group of virtual machines and a group of hosts. An affinity rule specifies that the members of a selected virtual machine DRS group can or must run on the members of a specific host DRS group. An anti-affinity rule specifies that the members of a selected virtual machine DRS group cannot run on the members of a specific host DRS group.
See VM-Host Affinity Rules for information about creating and using this type of rule.
■
Used to specify affinity or anti-affinity between individual virtual machines. A rule specifying affinity causes DRS to try to keep the specified virtual machines together on the same host, for example, for performance reasons. With an anti-affinity rule, DRS tries to keep the specified virtual machines apart, for example, so that when a problem occurs with one host, you do not lose both virtual machines.
When you add or edit an affinity rule, and the cluster's current state is in violation of the rule, the system continues to operate and tries to correct the violation. For manual and partially automated DRS clusters, migration recommendations based on rule fulfillment and load balancing are presented for approval. You are not required to fulfill the rules, but the corresponding recommendations remain until the rules are fulfilled.

64. While powering on a VM, you are getting different errors you should know how to troubleshoot these kind of errors?
65. What is VMware cloud director and why it is used?
Ans.
VCloud Director (vCD) is VMware Inc.'s cloud computing management tool. It manages Infrastructure as a Service (IaaS) architectures by monitoring and controlling various cloud-computing components, such as security, virtual machine (VM) provisioning, billing and self-service access. It focuses on private and hybrid cloud-computing infrastructures.

 VCloud Director doesn't provide a standalone cloud infrastructure. Rather, a vCD setup requires additional tools, such as an Oracle database and 64-bit Red Hat Enterprise Linux (RHEL) 5. And for advanced vCloud Director features, users must turn to several products and vendors:

  1. VShield Edge for security
  2. HyTrust Inc.'s Cloud Control for authentication federation
  3. Zenoss Inc. for advanced monitoring and reporting
  4. Aria System's Inc, which supplies billing management software.

66. What is Vshield and why it is used?
Ans.
VMware vShield App is a hypervisor-based application-aware firewall solution for virtual datacenters. vShield App plugs directly into VMware vSphere to protect against internal network-based threats and reduce the risk of policy violations  within the corporate security perimeter using application-aware firewalling with deep packet inspection and connection control based on source and destination IP addresses.

67. What is VMware Data Recovery(VDR)?
Ans.
VMware Data Recovery is a simple-to-deploy backup and recovery solution that businesses should consider using when they virtualize their infrastructure to provide the first line of data protection for their virtual environment.
VMware Data Recovery enables:
  • Full image backup of  virtual machines.
  • Full and incremental recovery of virtual machines plus recovery of individual files and directories.
VMware Data Recovery is composed of three main components: 
1) The user interface plug-in for VMware vCenter Server
2) The VMware Data Recovery virtual appliance that manages the backup and recovery process
3) The de-duplicated destination storage.  

68. What is the limitations of FC and iSCSI Datastore in VDR?
Ans.
69. How to do integrity check in VDR?
70. How you will disable ballooning in a VM?
Ans.
Disabling ballooning via the vSphere Client
To set the maximum balloon size to zero:

  • Using the vSphere Client, connect to the vCenter Server or the ESXi/ESX host where the virtual machine resides.
  • Log into the ESXi/ESX host as a user with administrative rights.
  • Shut down the virtual machine.
  • Right-click the virtual machine listed on the Inventory panel and click Edit Settings.
  • Click the Options tab, then under Advanced, click General.
  • Click Configuration Parameters.
  • Click Add row and add the parameter sched.mem.maxmemctl in the text box.
  • Click on the row next to it and add 0 in the text box.
  • Click OK to save changes.

Disabling ballooning via the Windows registry
To disable ballooning on the virtual machine:

  • Log into the guest OS.
  • Click Start > Run, type regedit, and press Enter. The Registry Editor window opens.
  • Navigate to: \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\VMMEMCTL
  • Change the Start key from 2 to 4.
  • Save the setting and restart the guest OS.

Disabling ballooning via VMware Tools uninstallation/reinstallation

  • Uninstall VMware Tools from the guest OS.
  • Reinstall VMware Tools using the Custom Settings option, and deselect the Memory Control Drivers.


71. What type of replication we should use while doing P2V (volume based or file based)?
Ans.
Volume Based

72. Does RDM format the LUN in VMDK or not or it create pointer file?
Ans.
It Creates a Pointer File.

73. Unable to start virtual center service what to troubleshoot and how?
74. VM is responding very slow. how to troubleshoot (like CPU contention, Storage latency, Memory issue.)?
75. We have taken snapshot and revert to the snapshot . now what will happen to existing snapshot , will it remove or will it exist?
Ans.

76. How to enable Paravirtualization in Disk and Network?
Ans. 
Installing VMware tools in guest operating system enable disk and network paravirtualization drivers.

77. How to check the storage, cpu, memory or disk related problem through ESXtop?
78. On Path Selection Policy (PSP) like fixed, MRU, RR. how it works in background?
Ans.

79. How to make vCenter Highly-Available?
Ans.
Installing vCenter Heartbeat software will make vCenter server Highly-Available.

80. What is Auto Deploy?
Ans.
vSphere Auto Deploy can provision hundreds of physical hosts with ESXi software. You can specify the image to deploy and the hosts to provision with the image. Optionally, you can specify host profiles to apply to the hosts, and a vCenter Server folder or cluster for each host.

 When a physical host set up for Auto Deploy is turned on, Auto Deploy uses a PXE boot infrastructure in conjunction with vSphere host profiles to provision and customize that host. No state is stored on the host itself. Instead, the Auto Deploy server manages state information for each host
Auto Deploy stores the information for the ESXi hosts to be provisioned in different locations. Information about the location of image profiles and host profiles is initially specified in the rules that map machines to image profiles and host profiles. When a host boots for the first time, the vCenter Server system creates a corresponding host object and stores the information in the database. 

 http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2005131
Extra Points-http://blog.mwpreston.net/2013/11/14/8-weeks-of-vcap-auto-deploy/

81. What is image builder?
Ans.
The ESXi Image Builder CLI is a set of PowerCLI cmdlets that you can use to manage vSphere image profiles and VIB packages, such as driver VIBs and update VIBs. You can also use Image Builder cmdlets to export an image profile to an ISO or offline depot ZIP file that you can use to install ESXi with a customized set of updates, patches, and drivers.
82. What is difference between template and clone? 
Ans.
A clone is a copy of a VM whereas a template is a master copy of a VM used to create many clones.
Cloning allows you to create a copy of the entire VM including its hardware, settings, installed software, etc. This can certainly save you time if you need to duplicate a VM.  If this needs to be done frequently, its probably a the best idea to turn it into a template.  This way the VM stays protected as templates cannot be powered on or edited.  By converting to a template you proved  a more secure way of preserving a VM config that you would like to deploy many times.
Extra Points-http://blog.mwpreston.net/vcp-5/vcp-5-objective-4-3-manage-virtual-machine-clones-and-templates/

83. Differentiate between static port binding and ephemeral port?
Ans.
Static binding

 When you connect a virtual machine to a port group configured with static binding, a port is immediately assigned and reserved for it, guaranteeing connectivity at all times. The port is disconnected only when the virtual machine is removed from the port group. You can connect a virtual machine to a static-binding port group only through vCenter Server.
Note: Static binding is the default setting, recommended for general use.

 Ephemeral binding

 In a port group configured with ephemeral binding, a port is created and assigned to a virtual machine by the host when the virtual machine is powered on and its NIC is in a connected state. The port is deleted when the virtual machine is powered off or the virtual machine's NIC is disconnected.

 You can assign a virtual machine to a distributed port group with ephemeral port binding on ESX/ESXi and vCenter, giving you the flexibility to manage virtual machine connections through the host when vCenter is down. Although only ephemeral binding allows you to modify virtual machine network connections when vCenter is down, network traffic is unaffected by vCenter failure regardless of port binding type.
Note: Ephemeral port groups should be used only for recovery purposes when you want to provision ports directly on host bypassing vCenter Server, not for any other case.

84. How many number of snapshot we can take?
Ans.
The maximum supported amount of snapshots in a chain is 32. However, VMware recommends that you use only 2-3 snapshots in a chain.

85. Explain DAVG, QAVG, KAVG and GAVG? what is the relation between them?
Ans.
86. How many displays ESXtop support?
Ans.
Changing views/displays is easy type the following keys for the associated views:
c = cpu
m = memory
n = network
i = interrupts
d = disk adapter
u = disk device (includes NFS as of 4.0 Update 2)
v = disk VM

p = power states

87. What is the difference between ESXtop and rESXtop?
Ans.
The resxtop and esxtop command-line utilities provide a detailed look at how ESX/ESXi uses resources in real time. You can start either utility in one of three modes: interactive (default), batch, or replay.

The fundamental difference between resxtop and esxtop is that you can use resxtop remotely, whereas you can start esxtop only through the service console of a local ESX host.

88. Differentiate between VMware HW version 7 and 10?
Ans.
Features of Virtual Machine Hardware Version 10

  • Enablement for new CPU Architectures
  • LSI SAS support for  Oracle Solaris 11 operating system
  • Support for New  type of advanced host controller interface AHCI (Advanced  Host Controller Interface)
  • Virtual-SATA controller now supports both virtual disks and CD-ROM devices.
  • Support upto 4 SATA controllers with 30 devices per controller with total of 120 devices (was limit of 60 in vSPhere 5.1)


http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1014006

89. ESXi falls in which type of hypervisor category and why?
Ans.
Type 1 hypervisor because it run in hardware ring 0.
90. Differentiate between VMXnet3 and e1000 driver?
Ans.
VMXNET 3: The VMXNET 3 adapter is the next generation of a paravirtualized NIC designed for performance, and is not related to VMXNET or VMXNET 2. It offers all the features available in VMXNET 2, and adds several new features like multiqueue support (also known as Receive Side Scaling in Windows), IPv6 offloads, and MSI/MSI-X interrupt delivery. For information about the performance of VMXNET 3, see Performance Evaluation of VMXNET3 Virtual Network Device. Because operating system vendors do not provide built-in drivers for this card, you must install VMware Tools to have a driver for the VMXNET 3 network adapter available.VMXNET 3 is supported only for virtual machines version 7

 E1000: An emulated version of the Intel 82545EM Gigabit Ethernet NIC. A driver for this NIC is not included with all guest operating systems. Typically Linux versions 2.4.19 and later, Windows XP Professional x64 Edition and later, and Windows Server 2003 (32-bit) and later include the E1000 driver.
Note: E1000 does not support jumbo frames prior to ESXi/ESX 4.1.

91. How to differentiate between Software and Hardware iSCSI HBA?
Ans.
Software iSCSI Adapter
A software iSCSI adapter is a VMware code built into the VMkernel. It allows your host to connect to the iSCSI storage device through standard network adapters. The software iSCSI adapter handles iSCSI processing while communicating with the network adapter. With the software iSCSI adapter, you can use iSCSI technology without purchasing specialized hardware.

 Hardware iSCSI Adapter
A hardware iSCSI adapter is a third-party adapter that offloads iSCSI and network processing from your host. Hardware iSCSI adapters are divided into categories.

 1)Dependent Hardware iSCSI Adapter
Depends on VMware networking, and iSCSI configuration and management interfaces provided by VMware.

 2)Independent Hardware iSCSI Adapter

Implements its own networking and iSCSI configuration and management interfaces.

92. In which case we prefer vSphere VI Client over New vSphere Web client?
Ans.
For Site Recovery Manager and vSphere Update Manager, we prefer vSphere VI Client over web client.

93. What is VMware vSAN?
Ans.
The first thing to understand is that the name is a bit of a misnomer. VSAN has got nothing to do with SAN in the traditional sense. Instead it leverages the local storage from a number of ESXi hosts which are part of a cluster. A distributed vsan Datastore is then created leveraging the local storage from each of the ESXi hosts. This can then be used for VM placement, and of course supports a range of core vSphere technologies like vMotion, DRS & vSphere HA.

 Virtual SAN is fully integrated with vSphere. It is an object based storage system and a platform for VM Storage Policies that aims to simplify virtual machine storage placement decisions for vSphere administrators. Its goal is to provides both high availability as well as scale-out storage functionality. It can also be thought of in the context of quality of service (QoS) in so far as VM Storage Policies can be created which defined the level of performance and availability required on a per virtual machine basis.
VSAN can be thought of as both a converged platform (of both compute and storage) as well as hybrid storage solution (since it leverages both SSDs and traditional spinning disks).

94. What is Software Defined Networking (SDN)?
Ans.
Software-defined networking (SDN) is an approach to networking in which control is decoupled from hardware and given to a software application called a controller.

The goal of SDN is to allow network engineers and administrators respond quickly to changing business requirements. In a software-defined network, a network administrator can shape traffic from a centralized control console without having to touch individual switches. The administrator can change any network switch's rules when necessary -- prioritizing, de-prioritizing or even blocking specific types of packets with a very granular level of control. This is especially helpful in a cloud computing multi-tenant architecture because it allows the administrator to manage traffic loads in a flexible and more efficient manner. Essentially, this allows the administrator to use less expensive, commodity switches and have more control over network traffic flow than ever before.

95. DPM is dependent on which feature?
Ans.
HA and DRS

96. Can HA work without vCenter server?
Ans.
YES

97. What is Shares and how it is being calculated?
Ans.
Shares specify the relative importance of a virtual machine (or resource pool). If a virtual machine has twice as many shares of a resource as another virtual machine, it is entitled to consume twice as much of that resource when these two virtual machines are competing for resources.
Shares are typically specified as High, Normal, or Low and these values specify share values with a 4:2:1 ratio, respectively. You can also select Custom to assign a specific number of shares (which expresses a proportional weight) to each virtual machine.
Specifying shares makes sense only with regard to sibling virtual machines or resource pools, that is, virtual machines or resource pools with the same parent in the resource pool hierarchy. Siblings share resources according to their relative share values, bounded by the reservation and limit. When you assign shares to a virtual machine, you always specify the priority for that virtual machine relative to other powered-on virtual machines.

Share Values shows the default CPU and memory share values for a virtual machine. For resource pools, the default CPU and memory share values are the same, but must be multiplied as if the resource pool were a virtual machine with four VCPUs and 16 GB of memory.

98. What is vMA?
Ans.
The vSphere Management Assistant (vMA) allows administrators and developers to run scripts and agents to manage ESXi hosts and vCenter Server systems. vMA is a virtual machine that includes prepackaged software, a logging component, and an authentication component that supports non-interactive login.
99. Define OVF?
Ans.
Open Virtualization Format (OVF) is an open standard for packaging and distributing virtual appliances or more generally software to be run in virtual machines.

The standard describes an "open, secure, portable, efficient and extensible format for the packaging and distribution of software to be run in virtual machines". The OVF standard is not tied to any particular hypervisor or processor architecture. The unit of packaging and distribution is a so-called OVF Package which may contain one or more virtual systems each of which can be deployed to a virtual machine.

100. What is Virtual Appliance? 
Ans.
Virtual appliances are ready-to-run virtual machines packaged with an operating system and software application. These self-contained appliances make it simpler to acquire, deploy and manage applications by eliminating underlying hardware and operating system dependencies.
However, I was able to accumulate only 100 questions, but VMware is not at all limited to above questionnaire. It is so vast and ever expanding, so please take above set of interview questions as an example ONLY and don't limit you're knowledge to above mentioned questions. 

 Disclaimer- Don't held me responsible, if you fail any vmware interview, after reading above questions. Also, refer VMware Technical Documentation for updated and correct information.
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1 comment:

  1. Cav Life JapanFebruary 5, 2014 at 2:21 AM

    Nice listing of questions, and answers for what's there at the moment!

    ReplyDelete

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