So if I run a df -h on my home server a particular line jumps out at me:
# df -h
Filesystem Size Used Avail Capacity Mounted on
/dev/ufs/root 496M 46M 410M 10% /
devfs 1.0K 1.0K 0B 100% /dev
/dev/ufs/tmp 496M 76K 456M 0% /tmp
/dev/ufs/usr 285G 235G 26G 90% /usr
/dev/ufs/var 1.7G 112M 1.4G 7% /var
Er, last I checked taking 235 from 285 leaves you with 50 - not 26. I know some rounding goes on here, but 24GB appears to be "missing"! It looks like in the cases of almost all the lines there is some hard disk space that is not accounted for, but in the case of /usr it's certainly the most noticeable.
/usr is mounted on the same logical drive that everything else is - which is a RAID-5 drive provided by three 160GB drives on a Highpoint controller.
Any ideas? Is there something I just don't get here? Are the measurements showing me two different things based on a cluster size (similar to the size vs. size on disk in Windows)?