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VMWare Interview Questions and answers -vMotion


1.What is vMotion?     Live migration of a virtual machine from one ESX server to another with Zero downtime . VMs disk files stay where they are (on shared storage)
2. What are the use cases of vMotion ?
  •     Balance the load on ESX servers (DRS
  •     Save power by shutting down ESX using DPM
  •      Perform patching and maintenance on ESX server (Update Manager or HW maintenance


3.  What are Pre-requisites for the vMotion to Work?

  •      ESX host must be licensed for VMotion
  •      ESX  servers must be configured with vMotion Enabled VMkernel Ports.    
  •      ESX servers must have compatible CPU’s for the vMotion to work
  •      ESX servers should have Shared storage (FB, iSCSI or NFS) and VM’s should be stored on that    storage.
  •      ESX servers should have exact similar network & network names
4. What are the Limitations of vMotion?
  •      Virtual machines configured with the Raw Device Mapping(RDM) for clustering features using vMotion
  •      VM cannot be connected to a CD-ROM or floppy drive that is using an ISO or floppy image stored on a drive that is local to the host server. The device should be disconnected before initiating the vMotion.
  •       Virtual Machine cannot be migrated with VMotion unless the destination swapfile location is the same as the source swapfile location. As a best practice, Place the virtual machine swap files with the virtual  machine configuration file.
  •       Virtual Machine affinity must not be set (aka, bound to physical CPUs).
5. Steps involved in VMWare vMotion ?
 
  • A request has been made that VM-1 should be migrated (or “VMotioned”) from ESX A to ESX B.
  • VM-1′s memory is pre-copied from ESX A to ESX B while ongoing changes are written to a memory bitmap on ESX A.
  • VM-1 is quiesced on ESX A and VM-1′s memory bitmap is copied to ESX B.
  • VM-1 is started on ESX B and all access to VM-1 is now directed to the copy running on ESX B.
  • The rest of VM-1′s memory is copied from ESX A all the while memory is being read and written from VM-1 on ESX A when applications attempt to access that memory on VM-1 on ESX B.
  • If the migration is successful, VM-1 is unregistered on ESX A. 

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