ESX4 VM with thin provisioned disk shows thick when a snapshot is taken..

[PredatorVI]

I have VM's that are all provisioned as "thin", but as soon as I take a snapshot, the VM "Edit Settings" shows that it is now "thick". We are running ESX 4.0. If I then remove the snapshot(s), the disk reverts back to "thin"

It doesn't appear that the disk really becomes thick in the source VM. Disk usage remains as expected.

The kicker comes when you try to clone a VM with the snapshot. If I don't change the default Disk Format from "Same format as source" to "Thin provisioned format", the clone becomes thick.

Cloning a single VM is not the problem since I can simply select "thin" when prompted.

The real problem comes when I clone an entire vApp. We are using vApps to group and contain complete testing environments. It is very convenient to clone the entire vApp. However, cloning a vApp does not prompt and ask how to treat the disk format for the clones and seems to take the default "Same format as source" which it now thinks is "thick"!

Is there a way to change the default behavior for cloning to "thin"? This would solve my problem, even though snapshots are f.u.b.a.r.-ing the disk format.

Otherwise I think this is a bug.

[lamw]

I ran into this issue a few weeks back and filed an SR with VMware, they actually know about this bug and would be fix in a future release. You're right that even though the UI displays as 'thick', it's still thin.

The easiest way to guarantee that you won't run into this issue is to clone from the CLI via scripted solution, that way you control exactly what is going on and you know that every clone whether that's an individual VM or a clone of a vApp that all subsequent clones will be 'thin' provisioned.

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William Lam

VMware vExpert 2009

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Twitter: @lamw

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