Redundant NFS storage setup (part 3) : The disappointing PERC5/E

[Matthias Saou]

Tino Schwarze wrote :

> On Thu, Jan 03, 2008 at 01:04:08PM +0100, Matthias Saou wrote:
> 
> > > I would suggest testing with a stripe size of 64kb instead of 128kb. We 
> > > are currently testing our HP servers with a P800 with similar 
> > > dissapointment, but found out that anything above a stripe size of 64kb 
> > > absolutely kills the performance (ofcourse no one would tell us that). I 
> > > believe it's based on a similar chip that the PERC5/E has.
> > 
> > I've just tested with 64k stripe size. Read speed is still
> > disappointingly low... 50-60MB/s where software RAID gives 310-330MB/s.
> > 
> > It seems like this is even less than with 128k stripe size, with a
> > single non-cached file read I get 80-110MB/s now, had up to 250MB/s
> > with 128k stripe size and... 320MB/s with software RAID.
> > 
> > But to be 100% sure, I need to wait for the background initialization
> > to finish, which will take a few hours. I'm not holding my breath,
> > though.
> 
> Are you using the latest megaraid_sas? I've seen speed improvements
> using the new driver.

Yes, on RHEL5.1 x86_64 rebuilt with dkms from the Dell provided
sources :

# modinfo megaraid_sas
filename:       /lib/modules/2.6.18-53.1.4.el5/extra/megaraid_sas.ko
description:    LSI Logic MegaRAID SAS Driver
author:         megaraidlinux at lsi.com
version:        00.00.03.16
[...]

On top of the RAID array, I use XFS :
# modinfo xfs
filename:       /lib/modules/2.6.18-53.1.4.el5/extra/xfs.ko
license:        GPL
description:    SGI XFS with ACLs, security attributes, realtime, large
block/inode numbers, no debug enabled
author:         Silicon Graphics, Inc.
srcversion:     BBB854051112D7CF26B397E
depends:        
vermagic:       2.6.18-53.1.4.el5 SMP mod_unload gcc-4.1

I always create the filesystem with :
# mkfs.xfs -f -L data -i size=512 /dev/sdb1

FWIW...

Matthias

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