From owner-freebsd-fs@FreeBSD.ORG Thu Jan 27 00:40:02 2005 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 EAF0716A4CE for ; Thu, 27 Jan 2005 00:40:02 +0000 (GMT) Received: from VARK.MIT.EDU (VARK.MIT.EDU [18.95.3.179]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6C4BF43D55 for ; Thu, 27 Jan 2005 00:40:00 +0000 (GMT) (envelope-from das@FreeBSD.ORG) Received: from VARK.MIT.EDU (localhost [127.0.0.1]) by VARK.MIT.EDU (8.13.1/8.13.1) with ESMTP id j0R0eDNN062659; Wed, 26 Jan 2005 19:40:13 -0500 (EST) (envelope-from das@FreeBSD.ORG) Received: (from das@localhost) by VARK.MIT.EDU (8.13.1/8.13.1/Submit) id j0R0eDDu062658; Wed, 26 Jan 2005 19:40:13 -0500 (EST) (envelope-from das@FreeBSD.ORG) Date: Wed, 26 Jan 2005 19:40:13 -0500 From: David Schultz To: Arne WXrner Message-ID: <20050127004013.GA62561@VARK.MIT.EDU> Mail-Followup-To: Arne WXrner , freebsd-fs@FreeBSD.ORG References: <20050126212838.GA61425@VARK.MIT.EDU> <20050126230346.7958.qmail@web41213.mail.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050126230346.7958.qmail@web41213.mail.yahoo.com> cc: freebsd-fs@FreeBSD.ORG Subject: Re: ufs+softupdates / consistency X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Jan 2005 00:40:03 -0000 On Wed, Jan 26, 2005, Arne WXrner wrote: > --- David Schultz wrote: > > ext2fs mounted async does not provide consistency; in fact the > > state of the disk can be almost arbitrarily inconsistent at any > > given time. Soft updates is supposed to provide performance > > comparable to async writes without the inconsistency problem. > > I'm not sure what it is about your setup that causes such a > > disparity. (Many factors such as the FS block size and ATA write > > caching can make a big difference.) > > > Somebody in list freebsd-performance@ opened a thread "FreeBSD 5.3 > I/O Performance / Linux 2.6.10 | Continued Discussion", where he > and one other state, that FreeBSD R4.11 beforms much better (twice > faster) than FreeBSD R5.3. > > Could the disparity I saw be caused by the SMPng project in R5.3? It's certainly possible. > > By the way, ext3fs uses journalling, which provides metadata > > consistency in a very different way from soft updates. You > > might also want to experiment with that to see if it works > better > > for your workload. > > > Hmm... I do not understand this hint. > > Does FreeBSD offer a journaling file system? No, although an interest in UFS+journalling has been expressed by someone who could make it happen. Also, Jean-Sebastien Pedron has been working on a port of ReiserFS to FreeBSD. > > > Are we already trying to issue write order requests for the > > > disc blocks (whose write order is arbitrary) sorted by sector > > > number (in order to move the disc heads as less as possible)? > > > The disc write cache could do that, but I disabled it in order > > > to decrease the probability of inconsistency. > > > > Hopefully you disabled it on both FreeBSD and Linux, so you're > > comparing apples to apples... > > > During the tests I enabled write cache in both settings, because I > did not know how to turn it off in KNOPPIX... > > Isn't it possible to simulate the hard disc write cache in kernel? The write caching will make a big difference. Sorry, but I don't know how to turn it off under Linux. Perhaps you could turn it on under FreeBSD for the purpose of your performance analysis.