From owner-freebsd-questions@FreeBSD.ORG Tue Mar 15 03:17:38 2005 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4B62116A4CE for ; Tue, 15 Mar 2005 03:17:38 +0000 (GMT) Received: from lakermmtao06.cox.net (lakermmtao06.cox.net [68.230.240.33]) by mx1.FreeBSD.org (Postfix) with ESMTP id 95F6F43D5A for ; Tue, 15 Mar 2005 03:17:37 +0000 (GMT) (envelope-from bob89@bobj.org) Received: from mail.bobj.org ([24.250.218.207]) by lakermmtao06.cox.net (InterMail vM.6.01.04.00 201-2131-118-20041027) with ESMTP id <20050315031734.KKLN21504.lakermmtao06.cox.net@mail.bobj.org> for ; Mon, 14 Mar 2005 22:17:34 -0500 Received: from bobj.dyndns.org ([192.168.132.161]) (AUTH: PLAIN bobj, ) by mail.bobj.org with esmtp; Mon, 14 Mar 2005 22:17:36 -0500 From: Bob Johnson To: freebsd-questions@freebsd.org Date: Mon, 14 Mar 2005 22:17:28 -0500 User-Agent: KMail/1.7.2 References: <200503141720.j2EHKqw16442@clunix.cl.msu.edu> In-Reply-To: <200503141720.j2EHKqw16442@clunix.cl.msu.edu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200503142217.29528.bob89@bobj.org> cc: Jerry McAllister cc: Svein Halvor Halvorsen cc: Jerry McAllister cc: "Loren M. Lang" Subject: Re: What's the easiest way to do a backup and verify? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 Mar 2005 03:17:38 -0000 On Monday 14 March 2005 12:20 pm, Jerry McAllister wrote: > > * Jerry McAllister [2005-03-14 10:30 -0500] > > > > > > [...] So then wouldn't a second dump of the same snapshot diffed to > > > > the tape device be a good for a verify? > > > > > > No, because the condition of the files that you are dumping the second > > > time is different from the first time. > > > > > > Most places cannot afford to make file systems completely unavailable > > > for periods of time long enough (several hours, up to a couple of > > > days) to allow dump to be run twice without any changes being made to > > > the file system. In FreeBSD 5.3 a snapshot can be created in parallel with a live filesystem. There is no need to stop normal operation while doing a backup of the snapshot (if I understand it correctly). Whether different files are consistent with each other (e.g. two database files simultaneously used by the same application) if you do a snapshot of a live filesystem is still likely to be a problem. > > > > Note the OP's use of the word "snapshot". I think he is right! Or if he > > isn't; it has nothing to do with the filesystem beeing changed, but > > rather something to do with the way the backup is written to tape. > > However, I do think snapshots could be used for exactly this. > > But, if he is writing a snapshot, then why is he using dump? > I think he was using the word snapshot to imply the dump file. > But, of course, I could be wrong. > I assumed that when he said "snapshot" he meant "snapshot", a frozen image of a filesytem I.E. see http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/snapshots.html And it seems to me that he's right. Two dumps of the same snapshot ought to have no diffs, so you could check the tape against the snapshot before deleting the snapshot. - Bob