From: Jens Axboe <axboe@suse.de>
To: Erik Slagter <erik@slagter.name>
Cc: linux-ide@vger.kernel.org
Subject: Re: Readahead with softraid1
Date: Fri, 8 Jul 2005 14:05:39 +0200 [thread overview]
Message-ID: <20050708120538.GH7050@suse.de> (raw)
In-Reply-To: <1120824029.23681.18.camel@localhost.localdomain>
On Fri, Jul 08 2005, Erik Slagter wrote:
> Hi,
>
> I am using softraid 1 on two sata disks and I'm trying to get the best
> possible performance. IMHO read actions (if properly addressed) should
> be split over the two drivers and performed independently. However, I
> don't notice anything to back this up. The read performance (with the
> dreaded hdparm) shows read performance on sda,sdb and md0 exactly the
> same.
>
> I've been playing a bit with readahead and it does matter a bit in that
> if I disable readahead for sda/sdb completely, the read rate for these
> goes completely down (to be expected) whilst the read rate on md0 stays
> the same (also a bit to be expected). Other combinations do not show any
> significant impact.
>
> I also played with the i/o scheduler and nr_requests (as from previous
> messages here).
>
> What am I doing wrong here???
raid1 doesn't split reads, currently you need more than one process
doing io to get a performance increase.
--
Jens Axboe
next prev parent reply other threads:[~2005-07-08 12:04 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-08 12:00 Readahead with softraid1 Erik Slagter
2005-07-08 12:05 ` Jens Axboe [this message]
2005-07-08 12:16 ` Danny Cox
2005-07-08 13:16 ` Erik Slagter
2005-07-08 13:30 ` Jens Axboe
2005-07-08 13:42 ` Danny Cox
2005-07-08 15:28 ` Greg Freemyer
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