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From: Christoph Hellwig <hch@infradead.org>
To: Wolfgang Denk <wd@denx.de>
Cc: Christoph Hellwig <hch@infradead.org>, linux-raid@vger.kernel.org
Subject: Re: Optimize RAID0 for max IOPS?
Date: Tue, 25 Jan 2011 16:35:23 -0500	[thread overview]
Message-ID: <20110125213523.GA14375@infradead.org> (raw)
In-Reply-To: <20110125184115.1119FB187@gemini.denx.de>

On Tue, Jan 25, 2011 at 07:41:15PM +0100, Wolfgang Denk wrote:
> > I don't think you even want a RAID0 in that case.  For small IOPs
> > you're much better off with a simple concatenation of devices.
> 
> What exactly do you mean by "conatenation"? LVM striping?
> At least the discussion here does not show any significant advantages
> for this concept:
> http://groups.google.com/group/ubuntu-user-community/web/pick-your-pleasure-raid-0-mdadm-striping-or-lvm-striping

No, concatenation means not using any striping, but just concatenating
the disk linearly, e.g.

 +-----------------------------------+
 |            Filesystem             |
 +--------+--------+--------+--------+
 | Disk 1 | Disk 2 | Disk 3 | Disk 4 |
 +--------+--------+--------+--------+

This can be done using the using the MD linear target, or simply
by having multiple PVs in a VG with LVM.

> 
> > Make sure to disable the disk write caches and if not using the newest
> > kernel also mount the filesystem with -o nobarrier.  With lots of small
> > I/Os and metadata intensive workloads that's usually a lot faster.
> 
> Tests if done recently indicate that on the other hand nobarrier causes
> a serious degradation of read and write performance (down to some 40%
> of the values before).

Do you have a pointer to your results?


  reply	other threads:[~2011-01-25 21:35 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-18 21:01 Optimize RAID0 for max IOPS? Wolfgang Denk
2011-01-18 22:18 ` Roberto Spadim
2011-01-19  7:04   ` Wolfgang Denk
2011-01-18 23:15 ` Stefan /*St0fF*/ Hübner
2011-01-19  0:05   ` Roberto Spadim
2011-01-19  7:11     ` Wolfgang Denk
2011-01-19  8:18       ` Stefan /*St0fF*/ Hübner
2011-01-19  8:29         ` Jaap Crezee
2011-01-19  9:32           ` Jan Kasprzak
2011-01-19  7:10   ` Wolfgang Denk
2011-01-19 19:21   ` Wolfgang Denk
2011-01-19 19:50     ` Roberto Spadim
2011-01-19 22:36       ` Stefan /*St0fF*/ Hübner
2011-01-19 23:09         ` Roberto Spadim
2011-01-19 23:18           ` Roberto Spadim
2011-01-20  2:48             ` Keld Jørn Simonsen
2011-01-20  3:53               ` Roberto Spadim
2011-01-21 19:34             ` Wolfgang Denk
2011-01-21 20:03               ` Roberto Spadim
2011-01-21 20:04                 ` Roberto Spadim
2011-01-24 14:40     ` CoolCold
2011-01-24 15:25       ` Justin Piszcz
2011-01-24 15:25         ` Justin Piszcz
2011-01-24 20:48         ` Wolfgang Denk
2011-01-24 20:48           ` Wolfgang Denk
2011-01-24 21:57         ` Wolfgang Denk
2011-01-24 21:57           ` Wolfgang Denk
2011-01-24 23:03           ` Dave Chinner
2011-01-24 23:03             ` Dave Chinner
2011-01-25  7:39             ` Emmanuel Florac
2011-01-25  7:39               ` Emmanuel Florac
2011-01-25  8:36               ` Dave Chinner
2011-01-25  8:36                 ` Dave Chinner
2011-01-25 12:45                 ` Wolfgang Denk
2011-01-25 12:45                   ` Wolfgang Denk
2011-01-25 12:51                   ` Emmanuel Florac
2011-01-25 12:51                     ` Emmanuel Florac
2011-01-24 20:43       ` Wolfgang Denk
2011-01-25 17:10 ` Christoph Hellwig
2011-01-25 18:41   ` Wolfgang Denk
2011-01-25 21:35     ` Christoph Hellwig [this message]
2011-01-26  7:16       ` Wolfgang Denk
2011-01-26  8:32         ` Stan Hoeppner
2011-01-26  8:42           ` Wolfgang Denk
2011-01-26  9:38         ` Christoph Hellwig
2011-01-26  9:41           ` CoolCold

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