I just rsynced everything on one fs to another of the same type and size.  Both underlying disks arw partitioned the same, and of the same model number.  What could be causing this discrepancy in availiable space?

[ BCrook@Desktop1 ~]$ df -h
Filesystem            Size  Used Avail Use% Mounted on
....
/dev/mapper/crypt     688G  561G  120G  83% /mnt/crypt
/dev/mapper/crypt2    688G  561G   92G  86% /mnt/crypt2
[BCrook@Desktop1 ~]$ mount
.....
/dev/mapper/crypt on /mnt/crypt type ext3 (rw)
/dev/mapper/crypt2 on /mnt/crypt2 type ext3 (rw)