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ONTAP Discussions

Very slow reclaim of space in volume


Hi all - If someone could help with this question would be awesome.

Here's our setup.

  • FAS3220 running 8.2.3p2 7-Mode
  • We have Exchange 2010 running on a Windows 2012 (non-R2) virtual machine on ESXi 5.5
  • The volumes are presented into the OS using LUNS via RDMs.
  • The particular drive we're seeing an issue with is a 780GB thin provisioned LUN presenting a 800gb thick provisioned volume.  it stores Exchange logs which are deleted (~300gb worth) nightly. 
  • We have enabled space_alloc on the LUNs to ensure when files (actually Exchange Logs) are deleted, we get the space back on the volume.
  • We keep only one nightly snapshot of the volume, and then it goes to SnapVault. So only 1 snap exists on the volume outside backup hours.

The issue:

We're seeing very very slow (sometimes none at all) space reclaimation on the volume after the logs are purged. We see the space come back in Windows immediately. 


For example, on one log volumes right now we have 200GB of data visible in Windows.

On that 800GB NetApp volume, NetApp shows 125GB available, 470gb Data used, and 204GB of snaps = 674GB total.


The controllers on the NetApps aren't being smashed (sitting around 50% or lower).


Is this descrepency due to the space reclaim in the background being very slow? or could there be some other issue? Is there a way to see the progress of the reclaim or expedite the reclaim process?


Any help would be great.


We've logged a call but it'll probbaly move slowly. 










This is likely related to SCSI UNMAP rather than space reclamation, I believe small in size deletions are done asynchronously where as large delations are done synchronously due to performance impacts but depends on Windows and the SCSI unmap commands sent.

Does deleting a large file say 20 - 30 GB result in the same delays to free up space ?


Hi Sparke
Usually snapshots deletion will havs retention period up to 24 hours .



Pleas explain

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