Vmware Snapshots and VM Performance

I am sure you have read or come across VMware best practices regarding snapshots. We use vDR in some of our backups in addition to Backup Exec to backup specific applications such as SQL and Exchange.

As a note, VMware snapshots are crash consistent and not application consistent. For that reason VMware do not recommend using snapshots on DC servers. To have an application consistent backup, Backup Exec and other third party backup application can do that for you.

Now back to our issue, running on multiple snapshots is bad. It is even worse when having multiple snapshots on one machine older than 3 days. Your machine would struggle reading from these multiple delta vmdk disks to recreate your data. These snapshots can get very large and can degrade the performance of the server immensely! We had this issue with an Exchange server that had 7 snapshots over 3 days old at various sizes, the server became unusable. The time it took to delete those snapshots were close to 10 hours and that wasn’t fun!

To avoid this crisis, setup alarms on your VCentre to cascade to all nodes in your cluster to alerts you for any VM running on snapshots.

There is a great KB article by VMware.

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