Disk space disappears to 0, then after a while I have free space

Question

I've been having this problem for quite a while and it happens occasionally and when it does it get very frustrating and I'm just trying to pin point what is causing it.

When it happens, the disk space gets exhausted all the way to 0 bytes available and when that happens, I can't even surf. But magically after a while, the disk space frees itself and I get my disk space back as shown below (copy pasted from console: look at /dev/disk0s2).

• In a span of 5 minutes, 1GB to 0 free space.
• After another minute I get my 1GB back. I have no Time Machine backups going (don't even have it configured), no Dropbox or other only syncing apps running and I don't think I'm doing anything out of the ordinary when it happens.

What would be the best way to track what is grabbing the disk space and later releasing it?

• OS X 10.9.3
• Macbook Pro (13", Mid 2009)

Console log:

elmaco:test thewheat$ date && df -h
Sun  8 Jun 2014 10:55:01 EST
Filesystem      Size   Used  Avail Capacity    iused      ifree %iused  Mounted on
/dev/disk0s2   232Gi  231Gi  1.0Gi   100%   60644234     264996  100%   /
devfs          219Ki  219Ki    0Bi   100%        756          0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%          0          0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%          0          0  100%   /home

elmaco:test thewheat$ date && df -h
Sun  8 Jun 2014 11:00:21 EST
Filesystem      Size   Used  Avail Capacity    iused      ifree %iused  Mounted on
/dev/disk0s2   232Gi  232Gi  6.7Mi   100%   60907509       1721  100%   /
devfs          219Ki  219Ki    0Bi   100%        756          0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%          0          0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%          0          0  100%   /home

elmaco:test thewheat$ date && df -h
Sun  8 Jun 2014 11:01:23 EST
Filesystem      Size   Used  Avail Capacity    iused      ifree %iused  Mounted on
/dev/disk0s2   232Gi  232Gi    0Bi   100%   60909230          0  100%   /
devfs          219Ki  219Ki    0Bi   100%        756          0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%          0          0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%          0          0  100%   /home

elmaco:test thewheat$ date && df -h
Sun  8 Jun 2014 11:02:22 EST
Filesystem      Size   Used  Avail Capacity    iused      ifree %iused  Mounted on
/dev/disk0s2   232Gi  231Gi  1.0Gi   100%   60647784     261446  100%   /
devfs          219Ki  219Ki    0Bi   100%        756          0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%          0          0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%          0          0  100%   /home

Update 1: So I've deleted some files so I have 6GB+ free and restarted but the behaviour still exists. I thought it could also be the swap file growing, but it stays consistently at 1GB when no space is available. Now I find this a bit strange as I have upgraded my RAM to 8GB for over a year now and I thought OSX would auto allocate the appropriate amount for the swap file and I don't recall ever doing anything to modify/restrict swap file sizes.

Is there a way to track what could be trying to grab 6GB of data and later free it? Or any log file that would help track this down?

elmaco:vm thewheat$ date && df -h
Sun  8 Jun 2014 13:31:46 EST
Filesystem      Size   Used  Avail Capacity  iused   ifree %iused  Mounted on
/dev/disk0s2   232Gi  232Gi    0Bi   100% 60909230       0  100%   /
devfs          205Ki  205Ki    0Bi   100%      708       0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%        0       0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%        0       0  100%   /home
/dev/disk0s7   136Gi   50Gi   79Gi    39%   251098 8817446    3%   /Volumes/Untitled 1

elmaco:vm thewheat$ date && df -h
Sun  8 Jun 2014 13:34:47 EST
Filesystem      Size   Used  Avail Capacity  iused   ifree %iused  Mounted on
/dev/disk0s2   232Gi  232Gi    0Bi   100% 60909230       0  100%   /
devfs          205Ki  205Ki    0Bi   100%      708       0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%        0       0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%        0       0  100%   /home
/dev/disk0s7   136Gi   50Gi   79Gi    39%   251098 8817446    3%   /Volumes/Untitled 1

elmaco:vm thewheat$ date && df -h
Sun  8 Jun 2014 13:36:40 EST
Filesystem      Size   Used  Avail Capacity  iused   ifree %iused  Mounted on
/dev/disk0s2   232Gi  226Gi  6.2Gi    98% 59272640 1636590   97%   /
devfs          205Ki  205Ki    0Bi   100%      708       0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%        0       0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%        0       0  100%   /home
/dev/disk0s7   136Gi   50Gi   79Gi    39%   251098 8817446    3%   /Volumes/Untitled 1

Update 2: So clearing up ~12GB of drive space managed to resolve the issue (now says 11GB free). My swap file is still 1GB so there isn't more space allocated to that.

That weird behaviour of eating up 6GB after a reboot is still perplexing, so I'm still curious to know what exactly was utilising the disk and would accept answers if I am able to recreate the scenario and see what exactly is requesting the space.

Answer 1

If you are saying you have 1GB of free memory then the problem is not what is grabbing that 1GB but the lack of memory in the first place.

This will get worse overtime because you are already hitting 0 bytes and operating system needs space to write out its files.

I strongly suggest you move essential files like photos a video media off to an external drive to free up some memory. These type of files being normally the largest and easiest to move. ( Do not delete any system files unless you know exactly what they are and removing them will not break you system)

Try and give yourself at least 10-15% free space as a minimum and keep at or above that.

Answer 2

kernel_task is doing that when it is paging out contents of RAM to disk.

Based on your virtual memory usage (8GB+ also written to your disk) you are going to want to keep at least 12GB of space free on your startup disk.

OS X uses virtual memory when it runs out of RAM, which means it moves some stuff from RAM to your disk and that is what is filling up the last bit of space.