The painless way to handle VMware ESX snapshots

If you work with virtual machines, you most likely already played around with snapshots. Its a really handy feature which lets you roll-back to a earlier stage of the lifetime of a system, just in case something goes wrong. During the extended lifetime of some VMs there might accumulate quite numerous snapshots which bloat the folder of the VM noticeably. One might think, that he just deletes the old snaps through ssh console access and the sky is blue again…?

If you just delete the old stuff by ssh console, you might run into some serious pains. The way here is merging the snapshots back to the vmdk. The way through the vSphere Client is the following: “Right-click on VM -> Snapshot -> Snapshot Manager -> Delete all”. Here is also where the trouble can start, in case you run out of storage. The way the snapshots get merged is the following:

Assume we have three snapshots:
Snap m, Size x
Snap n, Size y
Snap p, Size z

Step 1 of the merge:

  • Snap n transforms to Snap mn, Size x+y
  • Snap m deleted

Step2 of the merge:

  • Snap p transforms to Snap mnp, Size x+y+z
  • Snap mn deleted

Step3 of the merge:

  • Snap mnp gets merged with originating vmdk
  • Snap mnp deleted

So if you’re really tight in disk space, you might try to delete snapshot by snapshot instead of the “Delete all” option, starting with the newest.

If you have messed up totally and can’t delete the snapshots, a last effort could be to attach a Harddrive to your physical system (e.g. USB, eSATA you name it…) and use the VMware Converter to clone away the messed up VM in a clean vmdk.

The conclusion here is to carefully use snapshots and merging them proactively, avoiding to have too much system states flying around.

Useful links
Here you can find some backgrounds on snapshots:
KB article about running out of disk space during snapshot merge:

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