By default, ext4 formatted drive will automatically reserve 5% of the allocated space for root user, which reduce the total available space for other users or the application you may want to use that drive for.
This 5% ratio make sense on small volumes and purposes like the root (/) filesystem, but does not make any sense for a fileserver volume of 10 Tb.
Fortunately, this can be change easily and without any data loss using the following command :
tune2fs -m X /dev/device...
The “-m” option represent the percentage value you’d like to set the percentage of reserved blocks.
To completely disable the reserved space for root user, use “0” :
tune2fs -m 0 /dev/sdd1
To change the reserved blocks percentage to 1% :
tune2fs -m 1 /dev/sdd1
Below you can see the difference between the default 5% of reserved blocks VS 1% :
10Tb drive ext4 formatted with default 5% reservation
Filesystem Size Used Avail Use% Mounted on /dev/sdd1 10T 28K 9.5T 1% /mnt/data1
10Tb drive ext4 formatted with default 1% reservation
Filesystem Size Used Avail Use% Mounted on /dev/sdd1 10T 28K 9.9T 1% /mnt/data1