Question:root@localhost:~ $ df /dev/sdb1Filesystem ?1K-blocks ?Used Available Use% Mounted on/dev/sdb1 ?1922858352 ?23247088 1801935664 ?2% /mnt/external/sdb1
used+available = 1825182752
Size – 1825182752 ?= 97675600
Answer: 97675600 / 1825182752 = 5% this is the default reserved space for root user.