Recently I have had two servers that have been giving me a hard time when I try to back them up using VDR. These are a couple of the errors I am seeing

and this one…

These two VMs happen to both be Windows 2008 with Sql Server 2008. Now I could get a good backup of them with them turned off, but not while they were running. After some research there were a few ways which were suggested, but this is the only one I could get to work for my particular issue.

Disabling/Uninstalling VMware Tools VSS(Volume Shadow Copy):

Select Interactive Tools Upgrade.

Run the setup.

Select Modify

Expand VMware device Drivers. Navigate down to Volume Shadow Copy. Right-Click, and select “This feature will not be available”

What does disabling VMTools VSS actually do though>?

Well, VMTools VSS allows the VMware to quiesce the guest virtual machine. So uninstalling it prevents VMware from quiescing the virtual machine.

So then what does quiesce mean then?

Great Question! Well when a guest machine is quiesced, it’s processing is momentarily frozen for VMware to get a good consistent Snapshot of the guest. This way, no  read/writes are taking place during the snapshot process, which prevents file corruption.

This does Not mean that you are going to start corrupting all sort of files from disabling VMwareTools VSS. What it does mean is that there is a slight possibility that some files in the backup might be corrupted. However a snapshot with quiescing disabled is just like starting up a computer after the power cable had been pulled. Yes there is a possibility it might have some corruption, but in all likelyhood it probably won’t.

And at the end of the day, I would rather have a backup that has a very very small chance of corruption, then no backup at all.

Some Great References regarding similar issues!

A Great article about VM Snapshots and VSS

VMware articles regarding this

Understanding Snapshots

Trouble Shooting VSS quiesce related issues

Cannot create a quiesced snapshot because the snapshot operation exceeded the time limit for holding off I/O in the frozen virtual machine

Enabling Windows 2008 application-consistent quiescing on ESX 4.1

Categories: vCenterVMware


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