Thin Reclamation of Windows mount points

[Richard Siemers]

So, the practice of Thin Reclemation appears to be a dark art. Thin reclamation, is the process of taking back previously allocated space from a lun. This is good for cleaning up a VV that was migrated with a non-thin friendly method.

3PAR charges for the feature on their arrays, but provide no solutions on the host level to accomplish the task. To my knowledge only 2 file systems natively support this feature, Oracle's DBs and the VxFS included with Symantec Storage Foundations. For NTFS/FAT file systems, we're defered to a freeware utility called sdelete. I've been using this tool successfully for awhile but discovered the tool does not support mount points, just drives assigned to a letter. Bummer! Looking for alternatives I found many secure erase utilities, but did not find one that had the option to zero the data only. For example, cipher.exe is native to Windows XP and above, but, it secure erases with a pass of zeros, then ones, then random data, which will not relcaim our thinned free space.

Luckily, we found an OLD SCHOOL msdos solution to this problem... the SUBST command. By assigning a virtual drive letter to the path of the mount point, we were able to trick SDELETE into working.