From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q117TW09230203 for ; Wed, 1 Feb 2012 01:29:33 -0600 Received: from greer.hardwarefreak.com (mo-65-41-216-221.sta.embarqhsd.net [65.41.216.221]) by cuda.sgi.com with ESMTP id JluxSH7BaNPkWXcg for ; Tue, 31 Jan 2012 23:29:31 -0800 (PST) Received: from [192.168.100.53] (gffx.hardwarefreak.com [192.168.100.53]) by greer.hardwarefreak.com (Postfix) with ESMTP id 13CAD6C1A4 for ; Wed, 1 Feb 2012 01:29:30 -0600 (CST) Message-ID: <4F28E9DA.8030407@hardwarefreak.com> Date: Wed, 01 Feb 2012 01:29:30 -0600 From: Stan Hoeppner MIME-Version: 1.0 Subject: Re: Performance problem - reads slower than writes References: <20120130220019.GA45782@nsrc.org> <20120131020508.GF9090@dastard> <20120131103126.GA46170@nsrc.org> <20120131141604.GB46571@nsrc.org> <20120131202526.GJ9090@dastard> In-Reply-To: <20120131202526.GJ9090@dastard> Reply-To: stan@hardwarefreak.com List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: xfs@oss.sgi.com On 1/31/2012 2:25 PM, Dave Chinner wrote: > On Tue, Jan 31, 2012 at 02:16:04PM +0000, Brian Candler wrote: >> Here we appear to be limited by real seeks. 225 seeks/sec is still very good > > That number indicates 225 IOs/s, not 225 seeks/s. Yeah, the voice coil actuator and spindle rotation limits the peak random seek rate of good 7.2k drive/controller combos to about 150/s. 15k drives do about 250-300 seeks/s max. Simple tool to test max random seeks/sec for a device: 32bit binary: http://www.hardwarefreak.com/seekerb source: http://www.hardwarefreak.com/seeker_baryluk.c I'm not the author. The original seeker program is single threaded. Baryluk did the thread hacking. Background info: http://www.linuxinsight.com/how_fast_is_your_disk.html Usage: ./seekerb device [threads] Results for a single WD 7.2K drive, no NCQ, deadline elevator: 1 threads Results: 64 seeks/second, 15.416 ms random access time 16 threads Results: 97 seeks/second, 10.285 ms random access time 128 threads Results: 121 seeks/second, 8.208 ms random access time Actual output: $ seekerb /dev/sda 128 Seeker v3.0, 2009-06-17, http://www.linuxinsight.com/how_fast_is_your_disk.html Benchmarking /dev/sda [976773168 blocks, 500107862016 bytes, 465 GB, 476940 MB, 500 GiB, 500107 MiB] [512 logical sector size, 512 physical sector size] [128 threads] Wait 30 seconds............................. Results: 121 seeks/second, 8.208 ms random access time (52614775 < offsets < 499769984475) Targeting array devices (mdraid or hardware, or FC SAN LUN) with lots of spindles, and/or SSDs should yield some interesting results. -- Stan _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs