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Re: poor io performance with xfs+raid5

To: Mike Eldridge <diz@xxxxxxxxx>
Subject: Re: poor io performance with xfs+raid5
From: Austin Gonyou <austin@xxxxxxxxxxxxxxx>
Date: 25 Apr 2002 15:45:23 -0500
Cc: Steve Lord <lord@xxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <20020425154135.B14120@xxxxxxxxxxxxxxxx>
References: <20020425154135.B14120@xxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
What card is it, BTW?


On Thu, 2002-04-25 at 15:41, Mike Eldridge wrote:
> On Thu, Apr 25, 2002 at 03:19:05PM -0500, Steve Lord wrote:
> > Well, Duh! I should have seen that first time around, I get into the
> > habit of reading my email too fast!
> > 
> > We may be able to fix some things, if we can remake the filesystem.
> > First you need to know the stripe unit of your raid - we can feed
> > this into XFS to make it do stripe aligned allocations. This has
> > to be done by hand on linux. Take a look at the mkfs.xfs man page
> > and the section on sunit and swidth options. Probably bump your log
> size
> > up from the default somewhat, not sure how it ended up as 1839
> > that is scary.
> 
> RAID5 on this card offers only a 64K stripe size.  however, i will be
> recreating the array as RAID1 or RAID10, which offers stripe sizes from
> 64K to 1MB.  i'm not sure which is the best way to go.  i think that the
> best thing to do, considering additonal space requirements might be
> neccessary, is to go with multiple RAID1 arrays and let LVM do the
> striping.  any caveats here?
> 
> this particular box is a mail server and it handles a lot of i/o with
> pretty small files (< 64K).  i want to optimize for performance.
> unfortunately, this is also my *first* foray into xfs/lvm/raid, so i
> want to make sure i have as much information as possible before i carve
> it all in stone.
> 
> i need to go read some more about LVM...
> 
> as for the log, yeah, just over 7MB, i have no idea either.  info i have
> read suggests a 32MB log, but i'd like to use something bigger, perhaps
> 128MB.  any caveats to using a log of this size?
> 
> > You still have not said which kernel version you are running beyond
> 2.4,
> > unless I speed read over that too.
> 
> i did in a previous email.  :)
> 
> it's vanilla 2.4.18 with the xfs-1.1 release patches applied.
> 
> -mike
> 
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-- 
Austin Gonyou
Systems Architect, CCNA
Coremetrics, Inc.
Phone: 512-698-7250
email: austin@xxxxxxxxxxxxxxx

"It is the part of a good shepherd to shear his flock, not to skin it."
Latin Proverb

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