2 Apr 2010

Windows 2008 Hyper-V or Volume Shadow Copy Bug Part II

Following on from the problem I blogged about a couple of weeks ago, this is definitely a bug in Windows. From what we’ve been told it’s an inheritary, built-in limitation with VSS that prevents it from cleaning up after itself once 9,999 snapshots have been created. Therefore it only manifests if your server has created that many snapshots, so the explanation goes.

Now, not many people run snapshots frequently enough to encounter the problem but since our servers are running a backup every 30 minutes and there are 14 VHDs connected to Hyper-V we would run into the problem in just 15 days. That’s the explanation we were given but that doesn’t explain why after cleaning up the registry using devnodeclean and chkreg the registry will immediately start to bloat during the next backup. Hmmm. And we encountered symptoms (freezing) only after the first week – that’s less than 9999 snapshots. Hmm.

I’m hoping the engineers investigating this can come up with a permanent fix very soon.

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