VM Snapshots are not backups. They are just a change log of the original virtual disk. These cannot be considered as backup. There are a number of different reasons that one might use a snapshot for. One of the most used reasons would be for a software upgrade as using a snapshot allows an easy rollback to the machine state prior to the upgrade. If you have some other reasons leave a comment.
- The maximum supported amount in a chain is 32. However, VMware recommends only using 2-3 snapshots in a chain.
- No single snapshot can be used for more than 24-72 hours.
- This prevents snapshots from growing so large. This is because large snapshots cause issues when deleting/committing them to the original virtual machine disks. So the best method is to take the snapshot, make the necessary changes to the virtual machine, and delete/commit the snapshot as soon as proper working state of the virtual machine is verified.
- Be especially careful and decisive with snapshot use on high-transaction virtual machines (such as email and database servers). These snapshots tend to grow in size very quickly, filling datastore space. 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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- If using a third party product that takes advantage of snapshots (such as virtual machine backup software), regularly monitor systems configured for backups to ensure that no snapshots remain active for extensive periods of time.
- Snapshots should only be present for the duration of the backup process.
- Snapshots taken by third party software (called via API) usually may not show up in the vCenter Snapshot Manager. Routinely check for snapshots via the command-line.
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- Lot of snapshots in a chain or large sized snapshots cause decrease in the virtual machine and host performance.
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