From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: Readahead with softraid1 Date: Fri, 8 Jul 2005 14:05:39 +0200 Message-ID: <20050708120538.GH7050@suse.de> References: <1120824029.23681.18.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:18565 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S262494AbVGHMED (ORCPT ); Fri, 8 Jul 2005 08:04:03 -0400 Content-Disposition: inline In-Reply-To: <1120824029.23681.18.camel@localhost.localdomain> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Erik Slagter Cc: linux-ide@vger.kernel.org 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