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I’ll write a serie of 3 posts talking about the snapshots.

The first one (this one), will cover the fundamental of snapshots, best practices and when to use it.
The second one, will cover how to extract a list of guests with snapshots from your environment
The last one, will cover how to monitor the creation of the snapshots.

Let’s start…

What’s VMWARE snapshot ?
A snapshot is a picture of your system at the time the snapshot is taken. When you create a snapshot, a new DELTA file is create to store the changes that have occurred to the virtual machine since the snapshot was taken.

If you want to know more about snapshots, VMWARE has a good KB about it.

If you dont know how to create snapshots, check the video bellow

Vmware Snapshots Best practices

• 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 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.
• Confirm that there no snapshots present before a Storage vMotion.
• Confirm that there are no snapshots present (via command line) before increasing the size of any Virtual Machine virtual disk or virtual RDM.

Issues with Snapshots

• Old snapshots could grow so large as to cause issues when deleting/committing them to the original virtual machine disks.
• These snapshots can very quickly grow in size, filling datastore space.
• An excessive number of snapshots in a chain or snapshots large in size may cause decreased virtual machine and host performance.
• Migrating an ESX 3.x virtual machine with snapshots in powered-off or suspended state to another datastore might cause data loss and make the virtual machine unusable
• Increasing the size of a disk with snapshots present can lead to corruption of the snapshots and potential data loss.

So, when to use snapshots anyway

Snapshots are very good for testing new functionalities, installing new applications, patches, changing applications, in fact for every change you would make on the system that could take the system to fail. It’s a very fast recovery process, you just take an snapshot before you make any change , do you thing and if something goes wrong you can undo it very fast.
But remember, Commit snapshots on these virtual machines as soon as you have verified the proper working state of the process you are testing.|

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