From owner-freebsd-performance@FreeBSD.ORG Mon May 2 17:33:24 2005 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4800116A4D0; Mon, 2 May 2005 17:33:24 +0000 (GMT) Received: from critter.freebsd.dk (0x535c0e2a.sgnxx1.adsl-dhcp.tele.dk [83.92.14.42]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0947743D6A; Mon, 2 May 2005 17:33:23 +0000 (GMT) (envelope-from phk@critter.freebsd.dk) Received: from critter.freebsd.dk (localhost [127.0.0.1]) by critter.freebsd.dk (8.13.3/8.13.3) with ESMTP id j42HXIpe019123; Mon, 2 May 2005 19:33:18 +0200 (CEST) (envelope-from phk@critter.freebsd.dk) To: "Steven Hartland" From: "Poul-Henning Kamp" In-Reply-To: Your message of "Mon, 02 May 2005 17:43:16 BST." <003901c54f36$0c64ad40$b3db87d4@multiplay.co.uk> Date: Mon, 02 May 2005 19:33:18 +0200 Message-ID: <19122.1115055198@critter.freebsd.dk> Sender: phk@critter.freebsd.dk cc: Eric Anderson cc: freebsd-performance@freebsd.org cc: Robert Watson Subject: Re: Very low disk performance on 5.x X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 May 2005 17:33:24 -0000 In message <003901c54f36$0c64ad40$b3db87d4@multiplay.co.uk>, "Steven Hartland" writes: >Ok from what your saying it sounds like RAID on FreeBSD is useless >apart to create large disks. Now to the damaging facts the results >from my two days worth of testing: Now, cool down a moment and lets talk about what you _really_ have measured. You have measured the end to end performance: you include /dev/zero, dd(1), filesystem, disk device driver, hardware and disks. As such that is a fair end-user benchmark, but unfortunately it doesn't really tell us anything useful for the purpose of this discussion. If you are going to do a high-performance setup, you should not just take the "out-of-box" settings, you should optimize for the configurations particular features. Testing end-to-end means that we have very little to go from to find out where things went wrong in any one instance. But anyway: here are some questions which I wonder about ? Does the linux and FreeBSD filesystem offer the same semantics with respect to integrity ? Ie: if one is asyncronous mode the comparison is not a fair comparison. Just because you chose the default in each case doesn't mean you got the same thing. Does any of the drivers change the settings/modes of the controllers use of cache ? (this may be hard to determine without looking at driver sources. In particular, are you sure that the RAID-5 logical device was in the same exact state and location for each run ? Did you remember to disable all the debugging in FreeBSD 6-Current ? (see top of src/UPDATING) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.