Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 27 Jul 2001 10:17:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 27 Jul 2001 10:17:17 -0400 Received: from garlic.amaranth.net ([216.235.243.195]:22023 "EHLO garlic.amaranth.net") by vger.kernel.org with ESMTP id ; Fri, 27 Jul 2001 10:17:04 -0400 Message-ID: <3B6177DB.26C6D378@egenera.com> Date: Fri, 27 Jul 2001 10:16:59 -0400 From: "Philip R. Auld" Organization: Egenera Inc. X-Mailer: Mozilla 4.74 [en] (X11; U; Linux 2.2.19 i686) X-Accept-Language: en MIME-Version: 1.0 To: Alan Cox CC: kernel Subject: Re: ReiserFS / 2.4.6 / Data Corruption In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Original-Recipient: rfc822;linux-kernel-outgoing Alan Cox wrote: > > Its certainly a good idea. But it sounds to me like he is describing the > normal effect of metadata only logging. > Which brings up something I have been struggling with lately: Linux (using both ext2 and reiserfs) can show garbage data blocks at the end of files after a crash. With reiserfs this is clearly due to metadata only logging and happens say 3 out of 5 times. With ext2 the frequency is about 1 in 5 times, and more often that not it is simply zeroed data. Sometimes it is old data though. This is something that is not present in other unix filesystems as far as I can tell. If linux wants to be used in enterprise sites we can't allow old data blocks to be read. And ideally shouldn't allow zero blocks to be seen either, but this is somewhat less serious. I cannot reproduce this in ufs on either freebsd or solaris8. I have not tested it with xfs and jfs for linux yet (and don't have any native systems at hand.) I believe vxfs to have a mechanism to prevent this despite metadata only logging. reiserfs with full data logging enabled of course does not show this behavior (and works really well if you are willing to take the performance hit). The basic test I use is to run this perl script for a while (to make sure at least somehting has had a chance to get written out) and then power-cycle the machine. When it comes back a simple tail logfile will show the problem. I also run bonnie before hand to fill the disk with a known pattern so its easier to spot. linux is 2.2.16 and 2.4.2 from redhat 7.1. reiserfs is 3.5.33 and was tested only on 2.2.16. #!/usr/bin/perl use Fcntl; $count = 0; while (1) { #sysopen(FH, "/scratch/logfile", O_RDWR|O_APPEND|O_CREAT|O_SYNC) sysopen(FH, "/scratch/logfile", O_RDWR|O_APPEND|O_CREAT) or die "Couldn't open file $path : $!\n"; print FH "Log file line ", $count , " yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda yadda \n" ; close (FH); #print $count , "\n"; $count++; } ------------------------------------------------------ Philip R. Auld, Ph.D. Technical Staff Egenera Corp. pauld@egenera.com 165 Forest St, Marlboro, MA 01752 (508)786-9444 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/