VMware Interview Questions

Posted on May 1, 2015 Updated on May 7, 2015

1. ESX vs ESXi
   1. ESXi has no service console which is a modified version of RHEL
   2. ESXi is extremely thin hence results in fast installation + fast boot
   3. ESXi can be purchased as an embedded hypervisor on hardware
   4. ESXi has builtin server health status check
2. ESXi 4.1 vs ESXi 5.0 – Migration
   1. Local upgrade from CD
   2. VMware update manager (only supports upgrade of ESX/ESXi 4.x to ESXi 5.0)
3. ESXi 4.1 vs ESXi 5.0 – Features
   1. vSphere Auto deploy
   2. Storage DRS
   3. HA – Primary/secondary concept changed to master/slave
   4. Profile driven storage
   5. VMFS version – 3 → 5
   6. ESXi firewall
   7. VMware hardware version – 7 →  8
   8. VMware tools version – 4.1 → 5
   9. vCPU – 8 → 32
   10. vRAM – 256 → 1 TB
   11. VMs per host – 320 → 512
   12. RAM per host – 1TB → 2TB
   13. USB 3.0 support
   14. vApp
4. HA 5.0
   1. Uses an agent called FDM – Fault domain manager
   2. HA now talks directly to hostd instead of using vcenter agent vpxa
   3. Master/slave concept
   4. Master

1. monitors availability of hosts/VMs
2. manages VM restarts after host failure

• maintains list of all VMs in each host

1. restarting failed VMs
2. exchanging state with vcenter
3. monitor state of slaves

1. Slave

1. monitor running VMs and send status to master and performs restart on request from master
2. monitors master node health

• if master fails, participates in election

1. Two different heartbeat mechanisms – Network heartbeat and datastore heartbeat
2. Network heartbeat

1. Sends between slave and master per second
2. When slave is not receiving heartbeat from master, checks whether it is isolated or master is isolated or has failed

1. Datastore heartbeat

1. To distinct between isolation and failure
2. Uses ‘Power On’ file in datastore to determine isolation

• This mechanism is used only when master loses network connectivity with hosts

1. 2 datastores are chosen for this purpose

1. Isolation response

1. PowerOff
2. Leave Powered On

• Shutdown

1. vMotion
   1. vMotion enables live migration of running virtual machines from one host to another with zero downtime
   2. Prerequisites

1. Host must be licensed for vMotion
2. Configure host with at least one vMotion n/w interface (vmkernel port group)

• Shared storage (this has been compromised in 5.1)

1. Same VLAN and VLAN label
2. GigaBit ethernet network required between hosts
3. Processor compatibility between hosts

• vMotion does not support migration of applications clustered using Microsoft clustering service
• No CD ROM attached

1. No affinity is enabled
2. vmware tools should be installed

1. What is DRS? Types of DRS
   1. Distributed Resource Scheduler
   2. It is a feature of a cluster
   3. DRS continuously monitors utilization across the hosts and moves virtual machines to balance the computing capacity
   4. DRS uses vMotion for its functioning
   5. Types of DRS

1. Fully automated – The VMs are moved across the hosts automatically. No admin intervention required.
2. Partially automated – The VMs are moved across the hosts automatically during the time of VM bootup. But once up, vCenter will provide DRS recommendations to admin and has to perform it manually.

• Manual – Admin has to act according to the DRS recommendations

1. DRS prerequisites
   1. Shared storage
   2. Processor compatibility of hosts in the DRS cluster
   3. vMotion prerequisites
2. vMotion is not working. What are the possible reasons?
   1. Ensure vMotion is enabled on all ESX/ESXi hosts
   2. Ensure that all vmware pre requisites are met
   3. Verify if the ESXi/ESX host can be reconnected or if reconnecting the ESX/ESXi host resolves the issue
   4. Verify that time is synchronized across environment
   5. Verify that the required disk space is available
3. What happens if a host is taken to maintenance mode
   1. Hosts are taken to maintenance mode during the course of maintenance
   2. In a single ESX/ESXi setup, all the VMs need to be shutdown before getting into maintenance mode
   3. In a vCenter setup If DRS is enabled, the VMs will be migrated to other hosts automatically.
4. How will you clone a VM in an ESXi without vCenter
   1. Using vmkftools
   2. Copy the vmdk file and attach to a new VM
   3. Using VMware converter
5. What is vSAN?
   1. It is a hypervisor-converged storage solution built by aggregating the local storage attached to the ESXi hosts managed by a vCenter.
6. Recommended iSCSI configuration?
   1. A separate vSwitch, and a separate network other than VMtraffic network for iSCSI traffic. Dedicated physical NICs should be connected to vSwitch configured for iSCSI traffic.
7. What is iSCSI port binding ?
   1. Port binding is used in iSCSI when multiple VMkernel ports for iSCSI reside in the same broadcast domain and IP subnet, to allow multiple paths to an iSCSI array that broadcasts a single IP address.
8. iSCSI port binding considerations ?
   1. Array Target iSCSI ports must reside in the same broadcast domain and IP subnet as the VMkernel port.
   2. All VMkernel ports used for iSCSI connectivity must reside in the same broadcast domain and IP subnet.
   3. All VMkernel ports used for iSCSI connectivity must reside in the same vSwitch.
   4. Currently, port binding does not support network routing.
9. Recommended iSCSI configuration of a 6 NIC infrastructure ? (Answer changes as per the infrastructure requirements)
   1. 2 NICs for VM traffic
   2. 2 NICs for iSCSI traffic
   3. 1 NIC for vMotion
   4. 1 NIC for management network
10. Post conversion steps in P2V
    1. Adjust the virtual hardware settings as required
    2. Remove non present device drivers
    3. Remove all unnecessary devices such as serial ports, USB controllers, floppy drives etc..
    4. Install VMware tools
11. Which esxtop metric will you use to confirm latency issue of storage ?
    1. esxtop –> d –> DAVG
12. What are standby NICs
    1. These adapters will only become Active if the defined Active adapters have failed.
13. Path selection policies in ESXi
    1. Most Recently Used (MRU)
    2. Fixed
    3. Round Robin
14. Which networking features are recommended while using iSCSI traffic
    1. iSCSI port binding
    2. Jumbo Frames
15. Ports used by vCenter
    1. 80,443,902
16. What is ‘No Access’ role
    1. Users assigned with the ‘No Access’ role for an object, cannot view or change the object in any way
17. When is a swap file created
    1. When the guest OS is first installed in the VM
18. The active directory group, where the members will be ESXi administrators by default.
    1. ESX Admins
19. Which is the command used in ESXi to manage and retrieve information from virtual machines ?
    1. vmware-cmd
20. Which is the command used in ESXi to view live performance data?
    1. esxtop
21. Command line tool used in ESXi to manage virtual disk files?
    1. vmkfstools
22. Port used for vMotion
    1. 8000
23. Log file location of VMware host
    1. \var\log\vmware
24. Can you map a single physical NIC to multiple virtual switches ?
    1. No
25. Can you map a single virtual switch to multiple physical NICs?
    1. Yes. This method is called NIC teaming.
26. VMKernel portgroup can be used for:
    1. vMotion
    2. Fault Tolerance Logging
    3. Management traffic
27. Major difference between ESXi 5.1 and ESXi 5.5 free versions
    1. Till ESXi 5.1 free version there was a limit to the maximum physical memory to 32 GB. But from 5.5 onwards this limit has been lifted.
28. Maximum number of LUNs that can be attached to a host (ESXi 5.0)
    1. 256
29. Maximum number of vCPUs that can be assigned to a VM (ESXi 5.0)
    1. 32
30. What is CPU affinity in VMware? Its impact on DRS?
    1. CPU refers to a logical processor on a hyperthreaded system and refers to a core on a non-hyperthreaded system
    2. By setting CPU affinity for each VM, you can restrict the assignment of VMs to a subset of available processors
    3. The main use of setting CPU affinity is when there are display intensive workloads which requires additional threads with vCPUs.
    4. DRS will not work with CPU affinity
31. VMversion 4 vs VMversion 7
    1. Version 4

3. Runs on ESX 3.x
4. Max supported RAM 64 GB

• Max vCPUs 4

1. MS cluster is not supported
2. 4 NICs/VM
3. No USB Support

1. Version 7

4. Runs on vSphere 4.x
5. Max supported RAM 256 GB

• Max vCPUs 8

1. MS cluster is supported
2. 10 NICs/VM
3. USB support

41. What happens to the VMs if a standalone host is taken to maintenance mode?
    1. In case of standalone servers , VMware recommends that VMs should be powered off before putting the server in maintenance mode
    2. If we put the standalone host in maintenance mode without powering off the VMs, it will remain in the ‘entering maintenance mode’ state until the VMs are all shutdown
    3. When all the VMs are powered down, the host status changes to ‘under maintenance’
42. How can you edit a vm template?
    1. The VM templates cannot be modified as such
    2. First , the VM template have to be converted to a virtual machine
    3. After making necessary machines in the virtual machine, convert the virtual machine back to template
43. VMware hardware version comparison