This Tech OnTap article examines a relatively new NetApp technology: space reclamation. Space reclamation helps you conserve and re-use disk space already allocated to LUNs, and has been integrated into NetApp SnapDrive for Windows 5.0. To understand space reclamation, you have to remember that when you assign a LUN to a host, the host creates its own file system on the LUN and does its own bookkeeping. As a result, the host can have a very different idea of how much space it is currently using within the LUN than the storage system has.

Check out details on how space reclamation works and the potential impact on thin provisioning and snapshot copy creation at http://partners.netapp.com/go/techontap/matl/space_reclamation.html.