vSphere Snapshot Basics – Part 2

More about Snapshots

Snapshots are not backups, but backup software will leverage snapshots to take backups of the VM.

  • When you take snapshots the delta disks can potentially grow to the size of the original disk
  • When you take snapshots be careful because you can easily run out of storage space on the datastore

Snapshot Best Practices

If you plan to take snapshots

  • Do not over commit the datastore capacity
  • In fact you should be under commit by up to 30%
  • Do not create more than 1 snapshot
  • Do not keep snapshots for more that 1 day, in exceptional cases on production VMs (powered VMs) you may keep it up to 2 days

Difference between Clone and Snapshot

Clone is another copy of the virtual machine, where as a snapshot is a capture of point time state of the virtual machine. If you delete the virtual machine, the snapshot will also be deleted along with the it, however the clone will remain intact because its a separate copy.

vSphere Snapshot Basics – Part 1

What is a Snapshot?

  • It is a point in time state of the virtual machine
  • When you take a snapshot a delta disk gets created.
  • If you create another snasphot another delta disk will be created
  • The delta disk is mounted as ReadWrite (RW) whereas the original disk is mounted as ReadOnly (RO)
  • This delta disk is thin priovisioned disk, and grows in chunks of 16MB
  • After creation of Snapshot all disk writes within the VM go to the Snapshot-disk (delta disk) and not to the original disk (flat disk)

In vSphere, snapshots are based on “COW“

COW ==> Copy on Write Snapshots

In COW, all new writes always go to the delta disk.