NetApp DFM Snapshot Management – Remove Orphaned snapshots

Orphaned Snapshot Removal – Identify Orphans

I’ve been banging my head against the screen for the past few weeks looking at storage issues and finding orphaned volumes with reams of snapshots using up valuable disk space. In some cases it was due to manual intervention and a snapmirror or snapvault relationship was broken, in others it was caused by DFM creating new instances of the volume but not cleaning up old volumes and associated snapshots and in other cases, well I’ve no idea how they occurred. Hence why I’ve been slapping my brain around the inside of my skull. I’d be interested to know if this is still an issue with OCUM, answers on a postcard.

There’s no pretty way to clean up orphaned snapshots that are essentially owned by DFM. It’s messy, convoluted and requires that you’re very careful and precise about what you’re removing otherwise you’ll make things worse. There are a number of reasons why orphans can occur. One is down to  the way SnapProtect and the DFM work together. If a VM is deleted or moved to another volume and no other VM’s that are a part of that same backup subclient exist on that volume the snapshots will not age and will require a manual clean-up process. This seems to limit the use of automated DRS in VMware, but that’s a separate issue really. Another reason, and what looks to be the cause in my case, is that DFM has intermittent issues communication to the storage controller and thinks the volume doesn’t exist so it DFM may create a FlexClone of the volume and index it to have a new suffix while still being able to access the snapshots that were already captured. This can be caused by network drop outs out by the controllers or the CPUs maxing out and not being able to reply to DFM. I’m still investigating the cause of this. If a new storage policy was created in SnapProtect with these volumes assigned it would clear out the orphans but that would involve re-baselining the backups which is not something you’d want to do, unless of course that data had to value to you.

Read More