From: Neil Brown <neilb@suse.de>
Subject: Re: OT: RAID perf doldrums: advice/recommendations?
Date: Fri, 28 Oct 2005 13:34:47 +1000
Message-ID: <17249.40023.950260.948987@cse.unsw.edu.au>
References: <20051028032149.14201.qmail@web51905.mail.yahoo.com>
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Cc: nfs@lists.sourceforge.net
To: email builder <emailbuilder88@yahoo.com>
In-Reply-To: message from email builder on Thursday October 27
Sender: nfs-admin@lists.sourceforge.net
Errors-To: nfs-admin@lists.sourceforge.net

On Thursday October 27, emailbuilder88@yahoo.com wrote:
> Hello,
> 
>   Recently we turned on a RAID-backed NFS server that fell flat on its face
> as soon as it started to see even moderate activity (particularly IMAP
> traffic from Courier-IMAP).  Through help on the Courier mailing list, the
> problem appears to be very poor throughput to our hard drives (although
> systems is not my strong point, so I hope there is not something else I've
> overlooked).
> 
>   Our choice to go with consumer-grade hardware seems to have bit us hard. 
> We are using the oft-maligned 3Ware 85xx series RAID5 controller and three
> Hitachi Deskstar 7k250 (250GB) SATA drives.  The NFS serves up the mailstore
> for a system that does about 60 mail messages/min, plus IMAP against the
> mailstore (which is what brings the hurt), and some moderately (much more
> than Joe Bob's homepage, but not Slashdot) trafficed web content.  We were
> able to buy some time by moving our (ext3) journal off of the same device,
> fiddle with a couple NFS settings (nodiratime,noatime), but it is still
> woefully slow.

mounting the ext3 partition with 'data=journal' can help NFS service,
especially with the journal on a separate device.

> 
>   We are also quite curious about just running with software raid instead,
> since there seems to be a growing movement that claims there is no reason it
> cannot be as (or more) reliable and fast -- especially compared to the piece
> of $@^!% that we apparently got.  :)

Certainly worth a try.  It may not be as fast as some high-end raid
cards, it is unlikely to be slower than what you have.

NeilBrown


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