Did you know that most filesystems reserve a percentage of the available free space as an emergency reserve for when the disk becomes full? This is a great safety mechanism if you’re running critical applications or database, but in many cases all this reserved space winds up going to waste. Especially so in the case of today’s 2 & 3 Terabyte disks!
On a linux EXT filesystem, 5% is reserved for access only by the root user. Assuming you have a 2T disk this is approximately 100G reservation, which is total overkill if you ask me! Luckily it’s easy enough to adjust on-the-fly with the tune2fs command.
For this example I’m going to change the number of reserved blocks from the default of 5% to 1% on the filesystem mounted as /misc.
A simple
As you can see, there is 639G of free space on this filesystem.
Now, we use
Now we check the available space
Now we have 672G free. That’s 33G of storage we just got back for free!
Now, it may seem attractive to set this to 0% to squeeze the most possible free space from your drive, and under some circumstances this is perfectly safe to do. However, don’t set this to 0% if you have processes running as root that you want to continue running if the disk fills. Here’s a simple of thumb if you’re not sure. If you’ll loose irreplaceable data (or your job) if this filesystem goes casters up, don’t set to 0%.
from http://backdrift.org/freeing-disk-space-in-linux
On a linux EXT filesystem, 5% is reserved for access only by the root user. Assuming you have a 2T disk this is approximately 100G reservation, which is total overkill if you ask me! Luckily it’s easy enough to adjust on-the-fly with the tune2fs command.
For this example I’m going to change the number of reserved blocks from the default of 5% to 1% on the filesystem mounted as /misc.
A simple
df -h will show you free space minus the reserve.[root@foo ~]# df -h | grep misc Filesystem Size Used Avail Use% Mounted on /dev/sda5 789G 110G 639G 15% /misc
Now, we use
tune2fs -m 1 to change the percentage reserved to 1%[root@foo ~]# tune2fs -m 1 /dev/sda5 tune2fs 1.39 (29-May-2006) Setting reserved blocks percentage to 1% (2133291 blocks)
[root@foo ~]# df -h | grep misc Filesystem Size Used Avail Use% Mounted on /dev/sda5 789G 110G 672G 14% /misc
Now, it may seem attractive to set this to 0% to squeeze the most possible free space from your drive, and under some circumstances this is perfectly safe to do. However, don’t set this to 0% if you have processes running as root that you want to continue running if the disk fills. Here’s a simple of thumb if you’re not sure. If you’ll loose irreplaceable data (or your job) if this filesystem goes casters up, don’t set to 0%.
from http://backdrift.org/freeing-disk-space-in-linux
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