Interview Topics for VMware L3- Part-1

1- Snapshot hidden files

The Snapshot Manager shows no snapshots but there are delta files present.

#vim-cmd vmsvc/getallvms  — Get VM ID

#vim-cmd vmsvc/snapshot.get [VMID]                  Check Snapshot for Virtual Machine using VMID

#vim-cmd vmsvc/snapshot.create [VmId] [snapshotName] [snapshotDescription] [includeMemory] [quiesced]

#vim-cmd vmsvc/snapshot.create 3 snapshot1 snapshot 0 0

#vim-cmd vmsvc/snapshot.removeall [VMID]

2- Quiesced snapshots are when your VM’s have a VSS aware plugin that asks applications to enter a safe state before the snapshot occurs. This is to prevent grabbing things like Exchange and SQL in an inconsistent state.

-VSS will not run with dynamic disk

–       Memory Snapshot not possible if disk is Independent persistent(No delta file created ,but all changes to the disk are preserved when the snapshot is deleted.) or independent non persistent(only redo file created after restart changes discarded)

-Snapshot revert will power off snapshot and changes will be lost. snapshot will be still there.

-delete and delete all will consolidate to base disk.

3- HA Isolation address Advance setting (set manually)

das.isolationaddress and disable the use of the default gateway for isolation verification using the advanced setting das.usedefaultisolationaddress set to false.

4- Vmware update manager – fixed vs dynamic difference. -Fixed patched does not update automatically whereas dynamic patched updates when new patched arrives.

5- vds location in esxi – /etc/vmware/dvsdata.db

6- Changing queue depth Default queue Depth 64

For QLogic:


# esxcli system module list | grep qln

For Emulex:

# esxcli system module list | grep lpfc

For Brocade:

# esxcli system module list | grep bfa

Run one of below to set Queue Depth

For QLogic:

# esxcli system module parameters set -p ql2xmaxqdepth=64 -m qlnativefc

For Emulex:

# esxcli system module parameters set -p lpfc0_lun_queue_depth=64 -m lpfc

For Brocade:

# esxcli system module parameters set -p bfa_lun_queue_depth=64 -m bfa

reboot Host

Run this command to check changes-

# esxcli system module parameters list -m driver

7- Cpu affinity rule configured DRS will work ?- If DRS is On, CPU affinity option will not show ,to enable CPU affinity Disable DRS or configure partially or manual mode.

8- Different nas(NFS) vs iscsi vs san vs fcoe

Local Storage Not supported vMOtion,HA,DRS,RDM

NAS Over NFS not supported RDM and VM Cluster, rest all features are supported by all type of storage- Boot VM, vMOtion,HA,DRS, Storage API

9- unmap command (thin provision storage reclaiming technic)

10- SR-IOV Vs Direct I/O Path -SR-IOV offers performance benefits and tradeoffs similar to those of DirectPath I/O. DirectPath I/O and SR-IOV have similar functionality but you use them to accomplish different things.

With DirectPath I/O you can map only one physical function to one virtual machine. SR-IOV lets you share a single physical device, allowing multiple virtual machines to connect directly to the physical function.

11- Redundancy for VMware Network

Network Redundancy Using NIC Teaming. Using a team of two NICs connected to separate physical switches improves the reliability of a management network. Because servers connected through two NICs (and through separate switches) have two independent paths for sending and receiving heartbeats, the cluster is more resilient. To configure a NIC team for the management network, configure the vNICs in vSwitch configuration for Active or Standby configuration. The recommended parameter settings for the vNICs are:

Default load balancing = route based on originating port ID

Failback = No

After you have added a NIC to a host in your VMware HA cluster, you must reconfigure VMware HA on that host.

12- Disable Balloning – Go to Virtual Machine- EDit Setting- Options- Advance- General-Config Parameter- add row – sched.mem.maxmemctl and set Value 0

re-Enable Ballooning- Edit Virtual Machine Config file remove this line-  sched.mem.maxmemctl = “0”

14- New Feature in 6.5

  • 1-Vmware HA- Active passive and witnessed NODe
  • Asycronouse replication to Passive Node , DB syncronize
  • 2- Backup and Restore
  • 3- virtual Machine (EFI) Secure Boot
  • 4- Vmotion encryption
  • 5- Esxi secure boot using KMS cluster server
  • 6- VUM inbuilt in VCSA 6.5
  • 7- Autodeploy GUI configrution
  • 8- Predictive DRS
  • 9-Automated UNMAP
  • 10-Software iSCSI Static Routing Support -( Initiator and target can be in different subnet)
  • 11- Support for ERSPAN, ERSPAN mirrors traffic on one or more “source” ports and delivers the mirrored traffic to one or more “destination” ports on another switch. v

15- convert vmdk to Thin

# vmkfstools -i MMVOIP01_1-flat.vmdk -d thin MMVOIP01THIN.vmdk

# rm MMVOIP01_1-flat.vmdk

# mv MMVOIP01THIN.vmdk MMVOIP01_1-flat.vmdk

Or make a clone of VM- While making clone change disk type

Convert thin to thick – Go to datastor and select vmdk – Inflat

16- Recover Descriptor File from flat file-

1- Identify scsi controller

2- command- ls -l vmdk0-flat.vmdk

Output- root root 22323231231 oct  (copy disk size)

3- vmkfstools -c 22323231231 -a lsilogic thin temp.vmdk

4- this will create a new flat temp-flat.vmdk – remove this vmdk

5- rename temp.vmdk matching with flat.vmdk

6- vi newvmdk.vmdk  – change under Extent discriptor- .flat

17- Network latency

Network performance can be highly affected by CPU performance. Rule out a CPU performance issue before investigating network latency.

To determine whether the poor performance is due to network latency, Test the maximum bandwidth from the virtual machine with the Iperf tool.

While using Iperf, change the TCP windows size to 64 K. Performance also depends also on this value. To change the TCP windows size,

On the server side, enter this command:

– iperf -s

On the client side, enter this command.

– iperf.exe -c sqlsed -P 1 -i 1 -p 5001 -w 64K -f m -t 10 900M

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