Question regarding performance on big files.

[Mathieu AVILA]

  Hello XFS team,

I have run into trouble with XFS, but excuse me if this question has 
been asked a dozens times.

I'm am filling a very big file on a XFS filesystem on Linux that stands 
on a software RAID 0. Performance are very good until I get 2 "holes" 
during which my write stalls for a few seconds.
Mkfs parameters:
mkxfs.xfs -b size 4096 -s size 4096 -d agcount=2 -i size=2048
The RAID0 is done a 2 SATA disks of 500 GB each.

My test is just running "dd" with 8M blocks:
dd if=/dev/zero of=/DATA/big
(/DATA is the XFS file system)

The system is basically a RHEL5 with a 2.6.18 kernel and XFS packages 
from CentOS.

The problem happens 2 times: one time around 210 GB and the second time 
around 688 GB (hole in performance and response time is bigger the 
second time -- around 20 seconds)

Do you have any clue ? Do my mkfs parameters make sense ? The goal here 
is really to have something that is able to store big files at a 
constant throughput -- the test is done on purpose.

-- 
*Mathieu Avila*
IT & Integration Engineer
mathieu.avila at opencubetech.com

OpenCube Technologies http://www.opencubetech.com
Parc Technologique du Canal, 9 avenue de l'Europe
31520 Ramonville St Agne - FRANCE
Tel. : +33 (0) 561 285 606 - Fax : +33 (0) 561 285 635
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://oss.sgi.com/pipermail/xfs/attachments/20100920/155d07b0/attachment.htm>