From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 25 Sep 2001 09:06:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 25 Sep 2001 09:06:08 -0400 Received: from roc-24-169-102-121.rochester.rr.com ([24.169.102.121]:45446 "EHLO roc-24-169-102-121.rochester.rr.com") by vger.kernel.org with ESMTP id convert rfc822-to-8bit; Tue, 25 Sep 2001 09:05:59 -0400 Date: Tue, 25 Sep 2001 09:06:02 -0400 From: Chris Mason To: comandante@zaralinux.com, tegeran@home.com cc: Matthias Andree , linux-kernel@vger.kernel.org, reiserfs-list@namesys.com Subject: Re: [reiserfs-list] Re: [PATCH] 2.4.10 improved reiserfs a lot, but could still be better Message-ID: <327790000.1001423162@tiny> In-Reply-To: <3BB07EA2.4010804@juridicas.com> In-Reply-To: <20010924173210.A7630@emma1.emma.line.org> <20010924161518.KYHD11251.femail27.sdc1.sfba.home.com@there> <3BB07EA2.4010804@juridicas.com> X-Mailer: Mulberry/2.1.0 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, September 25, 2001 02:54:58 PM +0200 Jorge Nerín wrote: >> > Who says test.zero is a linear file and it's not scattered around the > whole disk and the fs layer is filling holes...? If it's the case the > write cache is a BIG win, just think that the fs writes a chunk at the > beggining of the disk, then another chunk at the end, then another near > the beginning, then... you get the picture, in this case the disk > reorders the seeks to best fit. > > If you want to try a REAL linear write do a dd if=/dev/zero of=/dev/hde7 > or whatever unused partition you have. > Exactly, especially since during the dd you're going to seek back to the log for a few commit writes. >>From a filesystem point of view, I've spent hours and hours getting reiserfs to order the writes correctly to keep data consistent after a crash. Turning on writeback caching without a battery backup more or less throws all that work out the window. Don't do it. For some people, a UPS counts as a battery backup, but there are lots of reasons that doesn't fly in any kind of production environment. If your job somehow depends on the data being safe, just get a raid controller with batter backed cache. -chris