Tuesday, December 4, 2012

Best practices for virtual machine snapshots in the VMware environment

  • Snapshots are not backups. As the snapshot file is only a change log of the original virtual disk, do not rely upon it as a direct backup process. The virtual machine is running on the most current snapshot, not the original vmdk disk files.
  • Snapshots are not complete copies of the original vmdk disk files. The change log in the snapshot file combines with the original disk files to make up the current state of the virtual machine. If the base disks are deleted, the snapshot files are useless.
  • Snapshot files can grow to the same size as the original base disk file, which is why the provisioned storage size of a virtual machine increases by an amount equal to the original size of the virtual machine multiplied by the number of snapshots on the virtual machine.
  • The maximum supported amount in a chain is 32. However, VMware recommends that you use only 2-3 snapshots in a chain.
  • Use no single snapshot for more than 24-72 hours. This prevents snapshots from growing so large as to cause issues when deleting/committing them to the original virtual machine disks. Take the snapshot, make the changes to the virtual machine, and delete/commit the snapshot as soon as you have verified the proper working state of the virtual machine.

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