When you format a new partition with EXT4FS, 5% of the available space is reserved for root things. So basically the df command will show 5% less available. I noticed this while backing up stuff from my fileserver to a drive on my desktop. My desktop was saying I had 0% free, but was still able to put things on it, probably because I was doing it as root. Anyways, you can see how much is being reserved on your partition with “dumpe2fs -h /dev/sd??”. If you want to make the reserved space non-reserved, just run “tune2fs -m0 /dev/sd??”. Where the “??” is the drive and partition number. I would do this on any partitions used for storing just files. This can also be done while the partition is actively being used. As in, it can be done online and does not have to be done offline.
server ~ # df /dev/sdb1 Filesystem Size Used Avail Use% Mounted on /dev/sdb1 2.8T 2.3T 372G 86% /files
Change Reserved Space
server ~ # dumpe2fs -h /dev/sdb1 | grep "Reserved block count" Reserved block count: 36620684 server ~ # tune2fs -m0 /dev/sdb1 Setting reserved blocks percentage to 0% (0 blocks) server ~ # dumpe2fs -h /dev/sdb1 | grep "Reserved block count" Reserved block count: 0
server ~ # df /dev/sdb1 Filesystem Size Used Avail Use% Mounted on /dev/sdb1 2.8T 2.3T 512G 82% /files