Storage VMotion is one the great features in VMware ESX and this time we will keep a focus on Interview Questions on VMware Storage vMotion. There are many aspects in real environment were Storage vMotion saves life while fixing production issues.

What is Storage VMotion?

Storage VMotion is Storage VMotion and in this process we do migrate virtual machines files (configuration files) and disks (vmdk files) from one Datastore to another Datastore Online with Zero Downtime.

I have created a full step by step flow of VMWare Storage vMotion Click Here

What are the use cases of Storage VMotion ?

  • Migrating from Old storage to new storage systems or migrating to different vendor storage without downtime to VM’s.
  • Performing Scheduled activity like storage upgrades on the source Datastore (which is made of external Storage 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.

There are many more scenarios these above are few examples

What are Pre-requisites for the Storage VMotion 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 Storage VMotion
  • You need make sure you have enough space of the destination datastore to move the files and disks of Virtual machines.

What are the Limitations of Storage VMotion?

  • Virtual machines with snapshots cannot be migrated using Storage vMotion.
  • Virtual machine with virtual compatibility RDM (Raw Device Mapping) can be migrated with Storage VMotion. 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 are in progress.
  • Virtual Machine should be in powered off state if you want to migrate the VM simultaneously to different host and storage.

Steps involved in VMWare Storage vMotion ?

  • Storage vMotion copies all the files expect virtual machine disk and create the directory as same the Virtual Machine name on the destination storage/ datastore.
  • 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.

I have created a full step by step flow of VMWare Storage vMotion Click Here

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