From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sat, 15 Jul 2006 03:49:40 -0700 (PDT) Received: from mondschein.lichtvoll.de (ms2.lichtvoll.de [194.150.191.235] (may be forged)) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with ESMTP id k6FAnPDW020010 for ; Sat, 15 Jul 2006 03:49:26 -0700 Received: from localhost (dslb-084-056-076-199.pools.arcor-ip.net [84.56.76.199]) by mondschein.lichtvoll.de (Postfix) with ESMTP id 85260FA510 for ; Sat, 15 Jul 2006 12:47:05 +0200 (CEST) From: Martin Steigerwald Subject: XFS and write barrier Date: Sat, 15 Jul 2006 12:48:56 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200607151248.56603.Martin@lichtvoll.de> Sender: xfs-bounce@oss.sgi.com Errors-To: xfs-bounce@oss.sgi.com List-Id: xfs To: linux-xfs@oss.sgi.com Hello, I am currently gathering information to write an article about journal filesystems with emphasis on write barrier functionality, how it works, why journalling filesystems need write barrier and the current implementation of write barrier support for different filesystems. I have quite good informations on XFS already, but some questions remain: 1) Is it safe to use write barriers with 2.6.16 or should one use 2.6.17 instead? This relates to: ----------------------------------------------------------------------- commit b04ed21a1fdbfe48ee0738519a4d1af09589dfea Author: Nathan Scott Date: Wed Jan 11 15:32:17 2006 +1100 [XFS] Disable write barriers for now till intermittent IO errors are understood. SGI-PV: 912426 SGI-Modid: xfs-linux-melb:xfs-kern:202962a Signed-off-by: Nathan Scott ----------------------------------------------------------------------- What are those intermittent IO errors? I googled but did not find a discussion of this change. 2) I experienced three XFS corruptions in one week on 2.6.16 with enabled write caches, but (by default) disabled write barriers, but on 2.6.15 - with enabled write cache as well - it only very rarely got corrupted. Does anyone have any hint as to why this may have been the case? Thing is that the system went down, the kernel crashed while it was in use. I am suspecting that the kernel went down due to other instabilities and then XFS got corrupted by out of order writes. But it may also been related to a different IO path and / or changes in the write barrier implementation in the block layer. Any ideas? No worries, if not, I simply write so. ;) It just would be nice to know why. I know its difficult to retrospect especially as I do not have the syslogs from those occasions anymore. Regards, -- Martin 'Helios' Steigerwald - http://www.Lichtvoll.de GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7