From owner-freebsd-questions@FreeBSD.ORG Tue Nov 1 21:24:37 2005 Return-Path: X-Original-To: freebsd-questions@freebsd.org 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 007A516A41F for ; Tue, 1 Nov 2005 21:24:36 +0000 (GMT) (envelope-from user@dhp.com) Received: from shell.dhp.com (shell.dhp.com [199.245.105.1]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8D9A743D46 for ; Tue, 1 Nov 2005 21:24:36 +0000 (GMT) (envelope-from user@dhp.com) Received: by shell.dhp.com (Postfix, from userid 896) id D3EE131339; Tue, 1 Nov 2005 16:24:31 -0500 (EST) Date: Tue, 1 Nov 2005 16:24:31 -0500 (EST) From: user To: Chuck Swiger In-Reply-To: <4367DB06.5030400@mac.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: freebsd-questions@freebsd.org Subject: Re: two quick conceptual questions RE: rsync (and rsyncing snapshots) X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 Nov 2005 21:24:37 -0000 Chuck - thank you... On Tue, 1 Nov 2005, Chuck Swiger wrote: > rsync complains when the filesystem changes underneath it, but it will continue > to run. On the other hand, rsync is not going to safely maintain the > referential integrity of a complex file like a live database, but it's okay for > most other things including mbox's. Does it simply complain, or does that somehow alter (lessen) the integrity of the sync that is going on ? > > Related: it occurs to me that perhaps it would be better to snapshot the > > filesystem, mount the snapshot, and then rsync the snapshot. On the other > > hand, the filesystem is continuously altering the snapshot as files are > > destroyed or changed ... so perhaps this does not gain anything. Is > > rsyncing a snapshot of a busy filesystem always, ever or never easier than > > rsyncing the busy filesystem itself ? > > rsync'ing a snapshot is a fine idea. Ok - because _nothing_ would change, and thus rsync would not complain, etc. My gut is that while rsync performance might be increased, filesystem performance would be about the same, since all destructions and changes on the underlying filesystem are still being committed to the snapshot ... can you think of a reason why this would not only increase the rsync performance, but the overall FS performance while rsyncing ? > > Finally, am I correct that there are _only two_ rsync comparison methods - > > the default checksum method, and the --size-only method ? Am I correct > > that rsync _always_ looks at the timestamp first, and then applies either > > checksum or size comparison ONLY IF the timestamps are different ? > > No, rsync checks both timestamp and size or checksum. So you are saying even if the timestamps are identical, rsync will _still_ do either a size or checksum comparison ? That seems ... inefficient ? Is there a way to tell it "if the timestamps are identical, just move on" ?