From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id 38E197F37 for ; Mon, 18 Mar 2013 13:22:06 -0500 (CDT) Date: Mon, 18 Mar 2013 13:22:02 -0500 From: Ben Myers Subject: Re: Xfs_repair and journalling Message-ID: <20130318182202.GD22182@sgi.com> References: <51455408.4070801@hardwarefreak.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Subranshu Patel Cc: stan@hardwarefreak.com, xfs@oss.sgi.com Hi Subranshu, On Sun, Mar 17, 2013 at 05:12:36PM +0530, Subranshu Patel wrote: > What I understand is that, XFS being a journalling filesystem makes running > xfs_repair after a unclean unmount unnecessary. You are correct. > After a system crash or force power down, one can mount the filesystem > which causes the journal to be replayed and handles the half finished > writes. This is one part. But there can be other file corruption as well > and these can be handled by xfs_repair. As Dave mentioned, XFS only journals metadata. Unwritten cached file contents will not be recovered in this situation. > So the crux is to mount the filesystem so that journal will be replayed, > and then unmount the filesystem and run xfs_repair. (Assuming xfs_repair > may not be a mandatory step always) If you are set up correctly, (e.g. write caches are turned off on your disk) you shouldn't even need to unmount the filesystem an run xfs_repair. See this section of the xfs faq for more about write caches: http://www.xfs.org/index.php/XFS_FAQ#Q:_What_is_the_problem_with_the_write_cache_on_journaled_filesystems.3F > In case of EXT4, journal will not be replayed on performing mount. One need > to invoke fsck which performs journal playback and then other corruption > checks/recovery. I can't speak for ext4. I do think that your expectation that fsck/repair be able to replay a journal is pretty reasonable. That's just not how it is implemented here. In xfs, log recovery is in the kernel and xfs_repair knows just enough about the log to avoid clobbering your precious metadata when it needs to be recovered. There was some discussion in the past about making xfs_repair able to recover the log but I wouldn't expect that any time soon. Regards, Ben _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs