Re: 2 question about XFS fragmentation and _fsr: SPLITTED Q2:normal files, samba share

Janos Haar
2011-04-26T21:48:53Z

Note: I have splitted my previous letter for easyer discusion...
This have only Question-2 the storage with only normal files and samba
share.

----- Original Message -----
From: "Dave Chinner" <david@fromorbit.com>
To: "Janos Haar" <janos.haar@netcenter.hu>
Cc: <linux-xfs@oss.sgi.com>
Sent: Monday, April 11, 2011 11:42 PM
Subject: Re: 2 question about XFS fragmentation and _fsr

> On Mon, Apr 11, 2011 at 07:39:07PM +0200, Janos Haar wrote:
>> Hello list,

>> Question 2:
>> One of our customers have one storage wich is exactly the same like
>> the one wich is described on the Q1, but only used for samba storage
>> for storing media files (big files.)
>> I am sure, there is no torrent or similar, and i have told to the
>> customers on the beginning "don't write more files parallel, to
>> avoid fragmentation", but today the storage is >95% fragmented.
>
> Once again, what does 95% fragmented mean?

[root@Clarus-gl2k10-2 admin]# cat xfs_get_frag_ratio
echo loop0
xfs_db -c frag -r /dev/loop0
[root@Clarus-gl2k10-2 admin]# ./xfs_get_frag_ratio
loop0
actual 51179670, ideal 5914, fragmentation factor 99.99%

>
>> The customer sad, he only does file write one by one, and nothing more.
>> How can this be?
>
> Depends on your samba configuration to how it does writes. If it is
> conigured to do sync writes then it will have all sorts of
> fragmentation problems. So without more details about the workload,
> the kernel that is being used, the fragmentation occurring (xfs_bmap
> is your friend) and the samba config, there's little that can be
> suggested here.

[root@Clarus-gl2k10-2 ~]# uname -a
Linux Clarus-gl2k10-2 2.6.28.10 #6 SMP Thu Apr 29 01:00:58 CEST 2010 x86_64
x86_64 x86_64 GNU/Linux

In kernel, i have tried out the pdflush-patch wich let me set the number of
pdflushd-s to 8-64.
This was not a good idea i know that, but if i am right this have no effet
to the fragmentation because pdflush not works on the FS layer.
Or i have missed something?

[root@Clarus-gl2k10-2 ~]# smbd -V
Version 3.0.23c-2

smb.conf (filtered the # lines and the ; lines)

[global]
workgroup = WORKGROUP
server string = Gladiator-StreamLine-gl2k10-2
security = user
load printers = yes
cups options = raw
log file = /var/log/samba/%m.log
max log size = 50
dns proxy = no
[store]
......

The workload is one PC for "administration" namely filling up the storage,
and 2 client wich can reach the media files in RO mount point.
The customer knows about "only write on file at one time".

>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com

Thanks,
Janos