From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263544AbTLONfN (ORCPT ); Mon, 15 Dec 2003 08:35:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263571AbTLONfM (ORCPT ); Mon, 15 Dec 2003 08:35:12 -0500 Received: from pf138.torun.sdi.tpnet.pl ([213.76.207.138]:38418 "EHLO centaur.culm.net") by vger.kernel.org with ESMTP id S263544AbTLONfE convert rfc822-to-8bit (ORCPT ); Mon, 15 Dec 2003 08:35:04 -0500 From: Witold Krecicki To: Linux Kernel Mailing List Subject: raid0 slower than devices it is assembled of? Date: Mon, 15 Dec 2003 14:34:54 +0100 User-Agent: KMail/1.5.93 MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: 8BIT Message-Id: <200312151434.54886.adasi@kernel.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I've got / on linux-raid0 on 2.6.0-t11-cset-20031209_2107: /dev/md/1: Version : 00.90.01 Creation Time : Thu Sep 11 22:04:54 2003 Raid Level : raid0 Array Size : 232315776 (221.55 GiB 237.89 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 1 Persistence : Superblock is persistent Update Time : Mon Dec 15 12:55:48 2003 State : clean, no-errors Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Chunk Size : 64K Number Major Minor RaidDevice State 0 8 3 0 active sync /dev/sda3 1 8 19 1 active sync /dev/sdb3 UUID : b66633c2:ff11f60d:00119f8d:7bb9fc6c Events : 0.357 Disks are two ST3120026AS connected to sii3112a controller, driven by sata_sil 'patched' so no limit for block size is applied (it's not needed for it). Those are results of hdparm -tT on drives: /dev/md/1: Timing buffer-cache reads: 128 MB in 0.40 seconds =323.28 MB/sec Timing buffered disk reads: 64 MB in 1.75 seconds = 36.47 MB/sec /dev/sda: Timing buffer-cache reads: 128 MB in 0.41 seconds =309.23 MB/sec Timing buffered disk reads: 64 MB in 1.46 seconds = 43.87 MB/sec /dev/sdb: Timing buffer-cache reads: 128 MB in 0.41 seconds =315.32 MB/sec Timing buffered disk reads: 64 MB in 1.23 seconds = 52.04 MB/sec What seems strange to me is that second drive is faster than first one (devices are symmetrical, sd[a,b]2 is swapspace (not mounted at time of test), sd[a,b]1 is /boot (raid1)). What is even stranger is that raid0 which should be faster than single drive, is pretty much slower- what's the reason of that? -- Witold Krêcicki (adasi) adasi [at] culm.net GPG key: 7AE20871 http://www.culm.net