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From: Michael Monnerie <michael.monnerie@is.it-management.at>
Subject: Re: XFS over LVM over md RAID
Date: Fri, 10 Sep 2010 02:25:55 +0200
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Cc: Richard Scobie <richard@sauce.co.nz>

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On Freitag, 10. September 2010 Richard Scobie wrote:
> Limited testing using dd and bonnie++ shows no difference in write=20
> performance
=20
=46or dd it should always show the same, as you just sequentially write a=20
large file. Only with bonnie you would see differences due to stripe=20
sets, as the speed only drops when doing I/O not on boundaries and/or=20
smaller than the stripe size, as the stripe size is the smallest=20
possible I/O for the RAID.

I don't know why you don't see any difference with bonnie though.

=46WIW, a stripe set of 256k means you do read/write 256k from a single=20
drive on each I/O, then the next 256k from the next drive. I hope you=20
have very few small accesses and mostly very large files. If you'd use a=20
database on that system it would crawl...

=2D-=20
mit freundlichen Gr=FCssen,
Michael Monnerie, Ing. BSc

it-management Internet Services
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