--Ext3 using a lot more space than XFS?

Question

Hi,
although this question is related to my fileserver I put it in this forum as it's not related to networking in any way, I hope it fits.
So, I have a fileserver mostly acting as NAS. The main volume consits of 250GB+500GB as one LVM group. I have a second group of the same size for backup. I use rsync for backups, and both volumes contain exactly the same data, only difference is: main volume is formatted with XFS, backup volume is using Ext3 with journal=data.
df -h:
Dateisystem Größe Benut Verf Ben% Eingehängt auf
/dev/mapper/data-fileserver
699G 605G 94G 87% /mnt/fileserver
/dev/mapper/data--backup-fileserver
679G 606G 39G 95% /mnt/backup
I double checked both filesystems contain the same data, still there is a difference of 55 gigabytes in free space. How come?

Answer 1

Well mostly. I set it to 1% the numbers looked good and I thought it'd be okay, however after setting the reserved space to 0% I still missed 19GB. On a closer look we can see that the Ext3 filesystem is around 20GB smaller than the XFS one, and I can't really understand that:
[root@dude ~]# tune2fs -m 0 /dev/data-backup/fileserver
tune2fs 1.40.3 (05-Dec-2007)
Setze Verhältnis der reservierten Blöcke auf 0% (0 blocks)
[root@dude ~]# df -h
Dateisystem Größe Benut Verf Ben% Eingehängt auf
/dev/mapper/data-fileserver
699G 607G 93G 87% /mnt/fileserver
/dev/mapper/data--backup-fileserver
679G 606G 74G 90% /mnt/backup
Both LVM groups have the same size:
[root@dude ~]# lvm lvscan
ACTIVE '/dev/data-backup/fileserver' [689,64 GB] inherit
ACTIVE '/dev/data/fileserver' [698,64 GB] inherit
And
[root@dude ~]# tune2fs -l /dev/data-backup/fileserver
tune2fs 1.40.3 (05-Dec-2007)
Block count: 180785152
Since I haven't changed the standard block size of 4K this means we have 723140608 K of data, or 706192 MB or 689,64 GB which is exactly the size of the volumes. So still I wonder what happended to 19GB of space