df

reserved blocks

Get info

# tune2fs -l /dev/sdb1 | grep cou
Inode count: 21299200
Block count: 85196703
Reserved block count: 4259473
Mount count: 1
Maximum mount count: 26

# tune2fs -l /dev/sda1 | grep -i "block size"
Block size:               1024

Change it

# tune2fs -r 0 /dev/sdb1
Setting reserved blocks count to 0