From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932085AbWGGJi4 (ORCPT ); Fri, 7 Jul 2006 05:38:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932092AbWGGJi4 (ORCPT ); Fri, 7 Jul 2006 05:38:56 -0400 Received: from mail-in-09.arcor-online.net ([151.189.21.49]:47561 "EHLO mail-in-09.arcor-online.net") by vger.kernel.org with ESMTP id S932085AbWGGJiz (ORCPT ); Fri, 7 Jul 2006 05:38:55 -0400 From: Bodo Eggert <7eggert@elstempel.de> Subject: Re: ext4 features To: Trond Myklebust , Bill Davidsen , "J. Bruce Fields" , Theodore Tso , Thomas Glanzmann , LKML Reply-To: 7eggert@gmx.de Date: Fri, 07 Jul 2006 11:38:01 +0200 References: <6tVcC-1e1-79@gated-at.bofh.it> <6uXYv-3RG-1@gated-at.bofh.it> <6veG8-350-7@gated-at.bofh.it> <6vfiU-465-13@gated-at.bofh.it> <6vmNk-77r-23@gated-at.bofh.it> <6vnq7-7Tw-55@gated-at.bofh.it> <6vrN0-5Se-9@gated-at.bofh.it> <6vBsY-38p-9@gated-at.bofh.it> User-Agent: KNode/0.7.2 MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8Bit X-Troll: Tanz Message-Id: X-be10.7eggert.dyndns.org-MailScanner-Information: See www.mailscanner.info for information X-be10.7eggert.dyndns.org-MailScanner: Found to be clean X-be10.7eggert.dyndns.org-MailScanner-From: 7eggert@elstempel.de Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Trond Myklebust wrote: > On Wed, 2006-07-05 at 22:32 -0400, Bill Davidsen wrote: >> But with timestamps I need remember only one number, the time of my last >> backup. Skipping over the question of "who's idea of time" inherent in >> network filesystems. I compare all ctimes with the time of the last >> backup and do incremental on the newer ones. If we use versioning I have >> to remember the version for each file! In practice I really question if >> the benefit justified keeping all that metadata between backups. And if >> I delete a file and create another by the same name, what is it's version? > > You are completely missing the point. Our background is that all NFS > clients are required to use the mtime and ctime timestamps in order to > figure out if their cached data is valid. They need to do this extremely > frequently (in fact, every time you open() the file). If the changes to these files are very infrequent compared to nanoseconds, you'll only need the version during some nanoseconds, and only during runtime. Having a second-change-within-one-timeframe-flag(*) instead of versions will be enough to make NFS mostly happy and only penalize your users for one nanosecond, and it won't force version-keeping into the filesystem. And besides that, all other filesystems will profit even without having nanosecond resolution nor versioning (but they'll suffer for up to a whole second). *) TODO: Create a nice name -- Ich danke GMX dafür, die Verwendung meiner Adressen mittels per SPF verbreiteten Lügen zu sabotieren. http://david.woodhou.se/why-not-spf.html