1.What is vMotion?

Live migration of a virtual machine from one ESX server to another with Zero downtime called vMotion. 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 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 machines configured with the Raw Device Mapping(RDM) for clustering features using
•     VM cannot be connected to a CD-ROM or floppy drive that is using an ISO or floppy image
             restored on a drive that is local to the host server. The device should be disconnected before
             initiating the vMotion.
•      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.

So its all about vmotion.. Hope you find this blog benificial.. Thanks!!

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