Wednesday, 10 January 2018

VMware Snapshot Best Practices

We've been talking about Snapshots and I find that they are sometimes misunderstood.

I always use VMware's best practices when I use them, and also when I talk about them.

Do not use snapshots as backups.

The snapshot file is only a change log of the original virtual disk, it creates a place holder disk, virtual_machine-00000x-delta.vmdk, to store data changes since the time the snapshot was created. If the base disks are deleted, the snapshot files are not sufficient to restore a virtual machine.

Also if a VM is reverted back to a previous state, all files are restored to a previous state, we can't brick level individual files, also a lot of applications such as Microsoft Exchange server do not support Snapshots/Checkpoints (Hyper-V).

Maximum of 32 snapshots are supported in a chain. However, for a better performance use only 2 to 3 snapshots. 

The more snapshots per VM, the more storage we require and potentially each Snapshot could grow to the size of the -Flat.vmdk, also we are potentially taking a snapshot of the Memory state of the VM.

This then introduces multiple Read points per file, so there could be a performance hit.

Do not use a single snapshot for more than 72 hours.

The snapshot file continues to grow in size when it is retained for a longer period. This can cause the snapshot storage location to run out of space and impact the system performance.

When using a third-party backup software, ensure that snapshots are deleted after a successful backup.

Snapshots taken by third party software (through API) may not appear in the Snapshot Manager. Routinely check for snapshots through the command-line.

Snapshot Manager fails to detect snapshots of VMs (1026380)

For more information and additional knowledge base articles visit the:

Best practices for using snapshots in the vSphere environment (1025279)