What is a virtual machine (VM) snapshot and when would having one be useful?

A knowledge base article about What is a virtual machine (VM) snapshot and when would having one be useful? provided by the UC Berkeley IT Service Hub - Knowledge Portal

A snapshot is a reference to a VM's state from a specific point in time.  It can be useful when performing complicated application upgrades because they can serve as a safety net.  If things don’t go as planned you can roll back to a snapshot that was taken prior to starting the upgrade.  Snapshots can help save a lot of time and frustration. 

Keep in mind that snapshots for bIT managed and self-managed customers are available for only 2 weeks from the time they’re taken.  The 2 week time limit does include weekends and holidays.

 

This policy covers VMware ESXi/vCenter snapshots in the bCloud private environment. 

What are VM Snapshots-

VMware VM snapshots are a great feature in our VPS environment. Using snapshots is very flexible way of being able to go back in time and revert changes. These are useful for changes to OS, application and config files. Also our UC Backup application (Commvault) uses them for efficient backups due to change block tracking. 

What VM Snapshots are NOT-

VM Snapshots are not Backups!

This is the number one thing not to do. While it might be tempting to save your work in snapshots instead of creating a regular backup job via your backup software.

VM Snapshots best practices-

  • Do not use a single snapshot for more than 2 weeks. (Exceptions made on a case by case basis)
  • Maximum of 32 snapshots are supported in a chain. However, for better performance use only 2 to 3 snapshots (UTIL Storage)

Important considerations-

  • 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 (affect other VMs) and impact the system performance.
  • When using a third-party backup software, ensure that snapshots are deleted after a successful backup.
  • You cannot increase the size of the Virtual Machine disk while the VM is running on snapshot during powered ON/OFF status. Increment of VMDK disks running on snapshot should never be attempted even using CLI. 

Cloud Team Actions-

We utilize vROPs (vRealize Operations Manager) to track snapshots. If we find snapshots older than 2 weeks we will inform the owner of the VM and request they delete them. 

 

https://kb.vmware.com/s/article/1025279