Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759410AbZFPQI0 (ORCPT ); Tue, 16 Jun 2009 12:08:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753926AbZFPQIT (ORCPT ); Tue, 16 Jun 2009 12:08:19 -0400 Received: from stz-softwaretechnik.de ([217.160.223.211]:4938 "EHLO stlx01.stz-softwaretechnik.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753831AbZFPQIT (ORCPT ); Tue, 16 Jun 2009 12:08:19 -0400 X-Greylist: delayed 1458 seconds by postgrey-1.27 at vger.kernel.org; Tue, 16 Jun 2009 12:08:19 EDT Date: Tue, 16 Jun 2009 17:43:42 +0200 From: Ralf Gross To: linux-kernel@vger.kernel.org Subject: io-scheduler tuning for better read/write ratio Message-ID: <20090616154342.GA7043@p15145560.pureserver.info> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1283 Lines: 30 Hi, I'm trying to tune the kernel/io-scheduler for better read/write ratio on a Areca RAID0 device (4 disks, kernel 2.6.26, xfs fs). I can get 200 MB/s seq. writes and about the same for seq. reads. My problem is that if there are reads _and_ writes on this device, the write throughput is much higher than the read throughput (40 MB/s read, 90 MB/s write). The deadline scheduler sounded like the way to go for getting better read results, but reagardless which parameter I change, the ratio keeps the same. cfq, noop.. different paramter settings, but alway the same result. short: is there a way to tune the kernel/scheduler settings in a way to get a higher read throughput? Writes are not that important, basicially there are only two 30 GB files on the device/filesystem that are used to spool data for two LTO-4 tape drives. So I need a certain read speed to keep both drives streaming. While the data gets written to one file, I need at least 50 MB/s for reading from the other file and sent to the tape drive. Thanks, Ralf -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/