Comments on: WTFriday: What happens when Windows runs out of Disk Space?

By: Roland Pihlakas

Roland Pihlakas — Mon, 05 Dec 2016 07:34:06 +0000

NTFS does free some reserved metadata space when the disk gets full since with full disk this reserved metadata space would not be of use anyway.

A bigger curiosity for me is that NTFS also often eats away lot of space that really should be free - to the point of having zero free space left. That "eaten away" space is miraculously reclaimed after reboot so much that sometimes even over 100 GB may be free again, lets say for example on a 600GB drive. Closing open file handles to big files does help sometimes too, but not as much as rebooting.

By: Jet

Jet — Mon, 15 Sep 2014 20:44:26 +0000

George are you sure that "pagefile.sys" was missing in that partition? It could stay there even after you move it to another partition (it deletes after reboot?). And I suggest there was also "hiberfil.sys" (hibernation file) which takes a lot of space too. Or maybe that 600MB was in Recycle Bin?

This will probably make it more clear where are those mystic MBs: 1) Disable/Move page file to another partition, 2) Disable hibernation (cmd -> powercfg -h off) 3) Reboot, make sure these files are not there (delete if they exist): pagefile.sys, hiberfil.sys 4) Empty recycle bin, run CleanManager (cmd -> cleanmgr), remove old restore points 5) Fill!

Have you done all these steps? or maybe smtg was missing? (What about doing it again? ;))

By: Arne

Arne — Sun, 13 May 2012 17:52:46 +0000

had you disabled VSS and flushed all shadow copies ?

By: George Edison

George Edison — Sun, 11 Mar 2012 01:56:46 +0000

@Camilo: That's a reasonable suggestion except I explicitly moved the page file to a separate partition prior to performing this experiment - so removing / shrinking it wouldn't have freed up 300 MB of space on the partition that was filled.

By: Camilo Martin

Camilo Martin — Sun, 11 Mar 2012 01:52:43 +0000

Even with all the sound arguments here, I really think it's the page file. I don't think Windows will delete installers (it is actually dangerous to do that sometimes) nor that it will try to compress files suddenly, moreso because that wouldn't get you instant 300MB (unless it's faster than I expect and it's an SSD).

So I'm with MBraedley.

By: Ryan Lantzy

Ryan Lantzy — Fri, 09 Mar 2012 21:18:58 +0000

I believe some of the free space that you observed after your initial attempt to fill the drive was Windows purging it's installer cache.

In the location Windows is stored on the disk, there are all kinds of cached files from installed applications. I think this includes installers from Windows Update, .NET Framework, and other sources.

While not necessary, I think the OS keeps them around because they may come in handy for going back to a restore point or what not.

By: kinokijuf

kinokijuf — Fri, 24 Feb 2012 20:28:07 +0000

I am constantly getting those messages after I salvaged data from a broken (usb plug kept coming out) wd passport. Curse you, WDC for not making the enclosure removable. I need to buy a new external drive.

By: Bob Bobson

Bob Bobson — Fri, 24 Feb 2012 19:55:29 +0000

You want to know what happens when the system drive runs out of space? You should have just asked; I have had this happen countless times over the years.

The primary symptom (at least in XP) is that the user profile cannot be loaded and a new, temporary, blank one is created. This is extremely frustrating because it requires messing with the registry to reset the paths to point to the original/old user profile.

Also, if there is really no space (ie 0-1KB free), then Windows won’t load at all. That is, LSASS and/or CSRSS may crash and give an error. (In fact, all sorts of seemingly “critical” errors during Windows boot-up are simply due to low disk space and don’t really do much/any harm.)

Of course the solution is to free up at least 1MB or so of space so that you can boot into Windows at all, then from there you can try to free up more space.

By: Vitaly

Vitaly — Wed, 22 Feb 2012 15:56:18 +0000

By: Pearsonartphoto

Pearsonartphoto — Sun, 19 Feb 2012 15:07:23 +0000

I bet you that Windows was compressing some files in the background, or it had some kind of temporary files it was able to remove that aren't easily found...