<unknown> disk space on WS2008R2–vssadmin command

Seth B and I have racked our brains today on why a plain-Jane domain controller (just AD-DS role, no DNS, no DHCP, nothing else with any logging load) had <25% free disk space (16/67GB).  The weak-sysadmin-crutch-tool WinDirStat showed us an unfulfilling 15GB of <unknown> files.  WinDirStat explaination of <Unknown> space

Ok, run windirstat with an Admin token.  Sigh – 14.2GB.

So – it evidently is all in the system+hidden folder ‘System Volume Information’

Enter our friend vssadmin.exe.

Even though Shadow isn’t enabled in the GUI for drive C:, WS2008R2 does allow apps and perhaps service packs? to do a system restore point.

Sure enough – we had two – from Feb and October 2012. 

Trying to remove via vssadmin failed with an un-useful message “Error: Snapshots were found, but they were outside of your allowed context.  Try removing them with the backup application which created them.”

Ok — just *WHAT* application created them.  You know what, I don’t care, I just want my disk space back:

vssadmin resize shadowstorage /on=C: /For=C: /Maxsize=4GB

Ta-da!  Both of our shadows removed.  Our DC now has 36/67GB free (yes we deleted some other detritus).

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