From owner-freebsd-fs@FreeBSD.ORG Sat Jan 21 20:58:27 2006 Return-Path: X-Original-To: freebsd-fs@FreeBSD.ORG Delivered-To: freebsd-fs@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 34CBD16A41F for ; Sat, 21 Jan 2006 20:58:27 +0000 (GMT) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (lurza.secnetix.de [83.120.8.8]) by mx1.FreeBSD.org (Postfix) with ESMTP id 64FC443D45 for ; Sat, 21 Jan 2006 20:58:26 +0000 (GMT) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (dapatm@localhost [127.0.0.1]) by lurza.secnetix.de (8.13.4/8.13.4) with ESMTP id k0LKwJSl059338 for ; Sat, 21 Jan 2006 21:58:24 +0100 (CET) (envelope-from oliver.fromme@secnetix.de) Received: (from olli@localhost) by lurza.secnetix.de (8.13.4/8.13.1/Submit) id k0LKwJ9Q059337; Sat, 21 Jan 2006 21:58:19 +0100 (CET) (envelope-from olli) Date: Sat, 21 Jan 2006 21:58:19 +0100 (CET) Message-Id: <200601212058.k0LKwJ9Q059337@lurza.secnetix.de> From: Oliver Fromme To: freebsd-fs@FreeBSD.ORG In-Reply-To: <20060121172644.19851.qmail@web50914.mail.yahoo.com> X-Newsgroups: list.freebsd-fs User-Agent: tin/1.8.0-20051224 ("Ronay") (UNIX) (FreeBSD/4.11-STABLE (i386)) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.1.2 (lurza.secnetix.de [127.0.0.1]); Sat, 21 Jan 2006 21:58:25 +0100 (CET) Cc: Subject: Re: can snapshots become corrupted ? Is fsck'ing /dev/md0 sensible ? X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: freebsd-fs@FreeBSD.ORG List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 21 Jan 2006 20:58:27 -0000 Joe Schmoe wrote: > On Sat, 21 Jan 2006, Oliver Fromme wrote: > > Yes, the snapshot is probably still "dirty". But it > > shouldn't matter, because you can only mount it read-only > > anyway. > > Ok, yes, the snapshot can only be mounted read-only - > this is true. However, the snapshot itself (whether > mounted or not) is continually being changed as files > are being changed or deleted on the filesystem in > question. So if the snapshot is corrupt, and I start > making changes/deletions on the (now clean) > filesystem, then wouldn't there be problems ? That question would have to be answered by a snapshots expert. But I guess you're right, there are probably problems. > Ok, understood. However, once I do a full and > successful fsck on that filesystem, it is completely > safe again, regardless of how long or how often I ran > it while it was dirty, right ? Right, provided the dirtyness was only soft-updates related and the disks were reliable. > [...] > The second question I need to ask is, when I am > rsyncing this filesystem to a remote host, why is it > not a read-only operation ? My rsync process, because > this filesystem was the _source_, and not the > destination, should not have written anything to this > filesystem. However, it succeeded when the fs was > read-only (softupdates were off) and it failed when > the filesystem was read-write (softupdates on). Is > there some kind of manipulation of the source > filesystem that rsync does that would be equal to a > lot of writing to the source disk ? When you read from a file, its atime (access time) is scheduled for an update (unless the FS is mounted with the "noatime" flag). That's a write operation. So when you rsync a lot of files, quite a lot of meta data updates can pile up. That happens only if the FS is mounted read-write, of course. > It is my understanding that soft-updates only deal > with writes to the disk That's right. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way. "Being really good at C++ is like being really good at using rocks to sharpen sticks." -- Thant Tessman