I’m on the team that manages one of our largest (Windows-based) fileserver installations, on the order of nearly 3TB. Back when we crossed the 1TB threshold (two years ago), we decided to start mirroring the fileserver in another building, just to cover our butts in the event of a disaster (of the IT variety). We’ve weathered a few in the past.
The mirroring process required a little bit of space on each drive/LUN to store synchronization files. So going forward from that point, we sized all LUNs about 10% larger than the department request (and only charged each department the amount of their initial request).
It turned out that we didn’t have to allocate the additional space for the mirroring process. It’s extremely impractical to shrink a volume/drive, so how do we take the slack-space so that the departments don’t use more than what they’re paying for?
Enter the fsutil command-line utility (which has been around since Windows XP!).
So, for example, we have a 550GB volume/drive/LUN, the department only paid for 500GB, and we want to take the 50GB of “extra” space:
fsutil file createnew SystemFileDoNotDelete.dat 53687091200
That last number is a little annoying; the file size is in bytes. Who works in bytes anymore?
Anywho, the 10% slack space ended up being useful yesterday; one of the 500GB drives for the Marketing department became 100% full! This is totally insane to me, but luckily we were able to avoid any problems by temporarily allocating part of the slack space by resizing the “empty” file. Score one for unintended consequences.
