If you are using Ext2/3/4 as a filesystem, you might not be aware that the system reserves a certain percentage of disk for root processes by default.
While this is normally useful on boot drives, it is a major hindrance on storage drives. Debian reserves 5% by default. On a 1 TB drive, this equates to approximately 47 GB!
This can percentage can be altered using tune2fs and the -m argument, followed by the percentage of blocks you wish to reserve.
Read more →