Windows Server 2012 R2 – Resolving System Disk Filling Issues

disk-space-utilizationhard drivewindows-server-2012-r2xenserver

This is a bit of a strange issue – the usual troubleshooting steps don't seem to apply.

On a XenServer 6.2 host (with SP1), I have a guest VM that is running Windows Server 2012 R2 that functions as a file/print server. The VM is about a year old. It has a system drive that is 45gb and a data drive that holds a few hundred gigs of shared files.

This morning, the system drive slowly started marching towards full. Not slow, but not fast either. Anyway, it hit full and print jobs stopped working. Weird. I ran windirstat and cleaned up some old log files. Things were fine, but then it filled that space too.

So, at that point, I'm out of things to clear off the C drive. I ran Windirstat again and noticed that the total disk usage was actually only 16gb. Huh? Windows explorer still reports that the disk is fully full at this point.

I rebooted.

Windows explorer now shows the correct amount of free space. Awesome! Until I refreshed… and noticed there was less free space. And refresh again… and less free space.

It's not a fast leak, but still will "fill" the remaining space within about 2.5 hours. I say "fill" because re-running Windirstat on C: shows that only 16 gigs of data still exist.

Interesting things:

  • This doesn't happen on the data disk.
  • vssadmin list writers lists no
    snapshots
  • I uninstalled our backup software client (Unitrends 8)
  • We aren't using file shadow copies/previous versions
  • fsutil volume diskfree C: agrees with Windows Explorer
  • We have a different VM also running S2012R2 on this host that is not experiencing the same issue.
  • We're up to date on Windows Update

Thanks for any help or pointers you can give! I'd be happy to try and report just about anything. I phoned this in to Citrix support, and they have a small patch they want me to apply, but they also admitted that it doesn't fix the issue. They're pointing the finger and Windows itself right now.

To sum all this up in a question – what else could cause Windows Explorer to think a disk is growing, but wouldn't show up with WinDirStat?

Update:
The diskspace mismatch is fixed. Aparently WinDirStat (ran as Admin) still doesn't see the C:\Windows\System32\Spool folder. Weird, right? Anyway, there was a 16gb file jammed in there. It's gone now. I'll update tomorrow with whether or not we see disk size creeping like we did before (just now with more free disk space for it to creep into)

Best Answer

Any updates or new applications been installed?

I'd also look at C:\Windows\System32\LogFiles which is where some IIS and Windows Error Reporting logs go. I typically disable Windows Error Reporting because it's filled some of my drives before.

I'd check event logs for any hints and continue to run whatever folder/file sizing utility you can to inspect C:\ to see what directories are taking up the most space and growing.

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