From: Michael Weissenbacher <mw@dermichi.com>
To: xfs@oss.sgi.com
Subject: Re: Calculating swidth On A RAID6 Volume
Date: Tue, 20 Jul 2010 16:13:29 +0200 [thread overview]
Message-ID: <4C45AF09.5090901@dermichi.com> (raw)
In-Reply-To: <201007201522.39455@zmi.at>
Michael,
>> If that is the case, then here is what I would expect my values to
>> be: sunit = 512
>> swidth = 4608
>
> I think sunit should be as big as the RAID controllers stripe size, as
> it describes the smallest I/O XFS should do. So sunit=512 would make it
> possible that XFS writes a single sector, while the RAID controller
> needs to read/write 256KB with your stripe size, resulting in
> performance degradation. But I'm no XFS dev, so maybe wait for a
> clearing from someone who has deeper XFS knowledge than me.
>
> sunit=262144
> swidth=9
>
> Would be my suggestion for your setup.
>
IIRC sunit and swidth are both specified in units of 512 bytes (don't
ask me why) so a sunit value of 512 would mean 256KB stripe size which
is correct :-)
If i am right, the FAQ should be corrected (hopefully some dev can
confirm/deny it)
cheers,
Michael
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next prev parent reply other threads:[~2010-07-20 14:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-20 12:06 Calculating swidth On A RAID6 Volume Andrew Debenham
2010-07-20 12:40 ` Michael Weissenbacher
2010-07-20 13:22 ` Michael Monnerie
2010-07-20 14:13 ` Michael Weissenbacher [this message]
2010-07-20 14:44 ` Emmanuel Florac
2010-07-20 15:00 ` Michael Monnerie
2010-07-20 15:27 ` Emmanuel Florac
2010-07-21 6:54 ` Dave Chinner
2010-07-20 15:04 ` Michael Monnerie
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