How to tell where/how space is used?

[Francisco Reyes <lists@xxxxxxxxxxxxxxxx>]

New to Dragonfly and trying to use it as a backup machine.

Filesystem                            Size   Used  Avail Capacity  Mounted 
on
ROOT                                   53G  11G    42G    21%   /
devfs                                 1.0K 1.0K     0B   100%   /dev
/dev/serno/00000000000000000001.s1a   984M  53M   853M     6%   /boot
/pfs/@@-1:00001                        53G  11G    42G    21%   /var
/pfs/@@-1:00002                        53G  11G    42G    21%   /tmp
/pfs/@@-1:00003                        53G  11G    42G    21%   /usr
/pfs/@@-1:00004                        53G  11G    42G    21%   /home
/pfs/@@-1:00005                        53G  11G    42G    21%   /usr/obj
/pfs/@@-1:00006                        53G  11G    42G    21%   /var/crash
/pfs/@@-1:00007                        53G  11G    42G    21%   /var/tmp

So the OS sees 11G in use.

> cd /
> du -hd 1

38M    ./sbin
 0B    ./dev
 0B    ./mnt
1.5K    ./root
561M    ./usr
12M    ./bin
38K    ./proc
2.0K    ./tmp
9.4M    ./etc
53M    ./boot
 0B    ./pfs
3.9G    ./HFH
34M    ./var
1.0K    ./home
4.6G    .

Du is only seeing 4.6. Where is the rest? Used by snapshots? Is there a way 
to see the space in use because of snapthos?