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digitalfrost

Member

Registered: 2007-10-15

Posts: 10

--Ext3 using a lot more space than XFS?

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?

Zer0

Member

From: Windsor, ON, Canada

Registered: 2006-08-25

Posts: 298

Re: --Ext3 using a lot more space than XFS?

Ext3 partitions contain a used space of 5% for special reasons by default. It's a safety feature so root can log in even when the filesystem becomes 100% used.  You can change the percentage by looking up the Ext3 Filesystem Tips Wiki

hmm what do ya know.. I posted that part of the wiki *pats himself on the back*

digitalfrost

Member

Registered: 2007-10-15

Posts: 10

Re: --Ext3 using a lot more space than XFS?

Problem solved in less than an hour, I guess thats a 10/10. Thanks

Zer0

Member

From: Windsor, ON, Canada

Registered: 2006-08-25

Posts: 298

Re: --Ext3 using a lot more space than XFS?

So that was the issue?  I remember scratching my head on that one when I compared reiserfs with ext3 and ext3 took up a bunch of space on an empty drive.  I don't think many people are aware of this "feature" of ext3 using 5% space by default.

digitalfrost

Member

Registered: 2007-10-15

Posts: 10

Re: --Ext3 using a lot more space than XFS?

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

jacko

Member

Registered: 2007-11-23

Posts: 838

Re: --Ext3 using a lot more space than XFS?

does your read out's take into account for /tmp. I am not sure what I am really looking at, just asking a stupid question.

digitalfrost

Member

Registered: 2007-10-15

Posts: 10

Re: --Ext3 using a lot more space than XFS?

/tmp is on another harddrive, the two LVM groups are just for storing data. Besides, in this case it doesn't matter what is inside the filesystem as it's size is "to small" to begin with.