1. What is SvMotion?

Migration of a virtual machine files and disks from one datastore to another with Zero downtime.

2. What are the use cases of SvMotion ?Migrating from Old storage to new storage systems or migrating to different vendor storage without downtimeto VM’s.

Performing Scheduled activity like storage upgrades on the source Lun.
Converting VM disk type from Thick to Thin and Thin to Thick.
Migrating the critical virtual machines to high performance storage arrays to improve performance of virtual Machine.

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

ESX host in which virtual machine is running should have access to source and destination storage.
ESX host should have configured with the license for svMotion

4. What are the Limitations of SvMotion?

Virtual machines with snapshots cannot be migrated using Storage vMotion.
Virtual machine with virtual compatibility RDM can be migrated with svMotion.If you convert the mapping file, a new virtual disk is created and the contents of the mapped LUN are copied to this disk.
For Physical compatibility RDM, only mapping file can be relocated.
Virtual Machines cannot be migrated while the VMware tools installation tools is in progress.
Virtual Machine should be in powered off state if you want to migrate the VM simultaneously to different host and storage.

5. Steps involved in VMWare SvMotion ?

svMotion copies all the files expect virtual machine disk and create the directory as same the Virtual Machine name on the destination storage.
It uses Changed Block tracking to track the virtual machine disk. The change block tracking knows which region disk includes data. This data will be stored in bitmap and reside either in memory or in a file.

Pre-copies Virtual machine disk and swap file will start from the source to destination datastore as the first iteration. once it is completed, It only transfers the region which were modified or written after the first iteration.

ESX performs fast suspend and resume of the virtual Machine. The final changed regions will be copied to the destination  before the virtual Machine is resumed on the destination datastore.

Virtual Machine will continue running on the destination datastore and source file and disk will be deleted.

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