From: Peter Rabbitson <rabbit+list@rabbit.us>
To: thomas62186218@aol.com
Cc: soltys@ziu.info, mauermann@gmail.com, keld@dkuug.dk,
linux-raid@vger.kernel.org
Subject: Re: LVM on raid10,f2 performance issues
Date: Mon, 19 Jan 2009 08:28:20 +0100 [thread overview]
Message-ID: <49742B94.8090407@rabbit.us> (raw)
In-Reply-To: <8CB47EBD70FE9E8-AC4-981@WEBMAIL-DG06.sim.aol.com>
thomas62186218@aol.com wrote:
> Hi everyone,
>
> I too was seeing miserable read-performance with LVM2 volumes on top of
> md RAID 10's on my Ubuntu 8.04 64-bit machine. My RAID 10 has 12 x 300GB
> 15K SAS drives on a 4-port LSI PCIe SAS controller.
>
> I use:
> blockdev --setra 65536 /dev/md0
>
> And this dramatically increased my RAID 10 read performance.
>
> You MUST do the same for your LVM2 volumes for them to see a comparable
> performance boost.
>
> blockdev --setra 65536 /dev/mapper/raid10-testvol
>
This is incorrect. Only the readahead setting of the _last_ block device
matters. So in case you have a raid6 of 10 drives, with LUKS on top,
with LVM on top - only the readahead settings of the individual LVs
matter, nothing further down the chain is consulted.
next prev parent reply other threads:[~2009-01-19 7:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-01 0:00 LVM on raid10,f2 performance issues Holger Mauermann
2008-12-01 16:42 ` Keld Jørn Simonsen
2008-12-02 23:28 ` Holger Mauermann
2008-12-03 7:15 ` Keld Jørn Simonsen
2008-12-03 9:43 ` Michal Soltys
2009-01-19 1:24 ` thomas62186218
2009-01-19 7:28 ` Peter Rabbitson [this message]
2009-01-26 19:06 ` Bill Davidsen
2009-01-19 7:30 ` Michal Soltys
2009-01-19 12:17 ` Keld Jørn Simonsen
2009-01-19 12:24 ` Peter Rabbitson
2009-01-19 13:59 ` Keld Jørn Simonsen
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