Date: Mon, 29 Aug 2005 17:12:26 +0200 (CEST) From: Svein Halvor Halvorsen <svein-freebsd-questions@theloosingend.net> To: Norberto Meijome <freebsd@meijome.net> Cc: questions@freebsd.org Subject: Re: rsync and moving files [Re: backup w/ snapshots] Message-ID: <20050829170053.M3014@maren.thelosingend.net> In-Reply-To: <43131C85.1070100@meijome.net> References: <20050828234043.H22315@maren.thelosingend.net> <20050829161506.E2522@maren.thelosingend.net> <43131C85.1070100@meijome.net>
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* Norberto Meijome [2005-08-30 00:32 +1000] > isn't that the whole point of having a backup? to have *another* copy of your > files? Well, yes and no. The idea is that I have a main computer that I want to backup. I want the backup to be (a) remote, (b) incremental and (c) random-accessible. So I thought that every day my backup-server could rsync my main computer, creating a mirror of the relevant directory trees. Then, as soon as the rsync job completes, it takes a snapshot of the filesystem. This snapshot could be mounted r/o and nfs-exported back to the original computer. Now: If I have a file /foo/test on my main computer. After the first rsync-job this file will be copied, assigned an inode and put on the disk somewhere. If I change this file, a local snapshot will be smart enough to just store the changed sectors that this file now occupies. But: If I move the file from /foo/test to /bar/test on my main computer, rsync will create a BRAND NEW FILE in /bar (and delete the file in /foo, since I used the --delete option). Now this NEW file will have a new inode, and cover new sectors on disk. The snapshot will then tak considerable more diskspace. If I move a large directory tree this way, this will occupy huge amounts of diskspace. If I however, make the snapshot on my local disk, this is not a problem, as on this local filesystem /bar/test is not a new file. So how can I make rsync know that the files were just moved (renamed, relinked), and make rsync reflect this fact on the remote mirror? > and I guess that yes, if the files are new in the remote system, when you > take a snapshot the difference with the previous snapshot will be the size of > the new data The files aren't new. Their names are!
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