From owner-freebsd-fs@FreeBSD.ORG Thu Feb 19 05:33:36 2004 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3FBA016A4CE; Thu, 19 Feb 2004 05:33:36 -0800 (PST) Received: from relay.kiev.sovam.com (relay.kiev.sovam.com [212.109.32.5]) by mx1.FreeBSD.org (Postfix) with ESMTP id C562343D1F; Thu, 19 Feb 2004 05:33:35 -0800 (PST) (envelope-from dimitry@al.org.ua) Received: from [212.109.32.116] (helo=svitonline.com) by relay.kiev.sovam.com with esmtp (Exim 4.30) id 1AtoJ4-000HPn-1E; Thu, 19 Feb 2004 15:33:34 +0200 From: Dmitry Alyabyev To: freebsd-fs@freebsd.org Date: Thu, 19 Feb 2004 15:33:33 +0200 User-Agent: KMail/1.6 References: <200402181729.06202@misha-mx.virtual-estates.net> In-Reply-To: <200402181729.06202@misha-mx.virtual-estates.net> X-NCC-RegID: ua.svitonline MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <200402191533.33495.dimitry@al.org.ua> X-Scanner-Signature: e35cef5ed21d82303c208435479e4a86 X-DrWeb-checked: yes cc: performance@FreeBSD.org Subject: Re: strange performance dip shown by iozone X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: dimitry@al.org.ua List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 Feb 2004 13:33:36 -0000 On Thursday 19 February 2004 00:29, mi+mx@aldan.algebra.com wrote: > Hello! > > I'm trying to tune the amrd-based RAID5 and have made several iozone > runs on the array and -- for comparision -- on the single disk connected > to the Serial ATA controller directly. > > The RAID-based FS was newfs-ed with ``-b 65536'', as it is intended to > store very large files. The single-disk FS was newfs-ed with defaults. > > No softupdates were enabled on either, since those seem to degrade iozone > results slightly (iozone reads/writes a single file anyway). > > The filesystems displayed different performance (reads are better with > RAID, writes -- with the single disk), but both have shown a notable dip > in writing (and re-writing) speed when iozone used the record lengthes > of 128 and 256. Can someone explain that? Is that a known fact? How can > that be avoided? > > The machine is an amd64 running a fresh -current. The disks are 200Gb > SATAs. RAID5 consists of 6 of them. which stripe size of RAID5 did you use ? -- Dimitry