http://partners.netapp.com/go/techontap/matl/space_reclamation.html
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Space reclamation may be particularly useful in any environment that shows a large variance in the amount of data used. Systems used for queuing print jobs, e–mail, or standard file sharing are excellent candidates for space reclamation on a periodic schedule. Any system that has gone through a major change is also a good candidate for space reclamation. If you've performed database reorganization or made significant changes to a database because of archiving, space reclamation will likely recover a significant amount of data.
Getting Started with Space Reclamation
NetApp space reclamation technology has been integrated into NetApp SnapDrive® for Windows 5.0 and comes at no additional cost. SnapDrive makes it easy for Windows server administrators to manage NetApp SAN storage using either a wizard–based approach or through a command–line interface (SDCLI) that can be used in conjunction with management scripts and scheduling programs.
Using the SnapDrive GUI or SDCLI, you can periodically initiate the space reclamation process on your LUNs. The GUI tool will first determine how much space can be reclaimed and ask if you wish to continue. You can limit the amount of time the process will use to ensure that it does not run during peak periods.
Here are a few things to keep in mind when you run space reclamation:
- It's a good practice to run space reclamation before creating a Snapshot copy. Otherwise blocks that should be available for freeing will be locked in the Snapshot and not able to be freed.
- Because space reclamation initially consumes cycles on the host, it should be run during periods of low activity.
- Normal data traffic to the LUN can continue while the process runs. However, certain operations cannot be performed during the space reclamation process:
- Creating or restoring a Snapshot copy stops space reclamation.
- The LUN may not be deleted, disconnected, or expanded.
- The mount point cannot be changed.
- We don't recommend running Windows defragmentation.
