Bug 29097

Once, i had 700mb to remove from the disk to free space. I df(1)'d to
know what was the size of each partition.

Here is what i typed with resulting outputs. Give a look at /usr.

reel@zeus% df -h
Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/ad1s1a   116M    41M    66M    38%    /
/dev/ad0s1g   311M   129K   286M     0%    /source
/dev/ad1s1e   2.3G   1.4G   697M    67%    /usr
/dev/ad0s1e   678M   337M   287M    54%    /usr/src
/dev/ad0s1f   388M   4.2M   352M     1%    /var
procfs        4.0K   4.0K     0B   100%    /proc

reel@zeus% su root
Password:
(in /usr)
su-2.05# rm -r sounds/
su-2.05# df -h
Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/ad1s1a   116M    41M    66M    38%    /
/dev/ad0s1g   311M   129K   286M     0%    /source
/dev/ad1s1e   2.3G   1.4G   697M    67%    /usr
/dev/ad0s1e   678M   337M   287M    54%    /usr/src
/dev/ad0s1f   388M   4.2M   352M     1%    /var
procfs        4.0K   4.0K     0B   100%    /proc
su-2.05# sync
su-2.05# df -h
Filesystem    Size   Used  Avail Capacity  Mounted on
/dev/ad1s1a   116M    41M    66M    38%    /
/dev/ad0s1g   311M   129K   286M     0%    /source
/dev/ad1s1e   2.3G  1015M   1.1G    48%    /usr
/dev/ad0s1e   678M   337M   287M    54%    /usr/src
/dev/ad0s1f   388M   4.1M   352M     1%    /var
procfs        4.0K   4.0K     0B   100%    /proc

is that normal?
i need to sync to know the real size of my partitions?

Fix: 

No. maybe it's an error with the buffer size or such. So many informations
kept in cache without being written to disk naturally. That's odd.
How-To-Repeat: Same distro/release date. Try to remove a big directory from a disk.