From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <506DA0B4.5020208@redhat.com> Date: Thu, 04 Oct 2012 15:44:04 +0100 From: "Bryn M. Reeves" MIME-Version: 1.0 References: <506C5CD8.2070502@mohawksoft.com> <506CFA0B.4000006@tlinx.org> <506D055E.901@mohawksoft.com> <506D1931.4040102@tlinx.org> <506D624A.5070104@mohawksoft.com> In-Reply-To: <506D624A.5070104@mohawksoft.com> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] access or interface to list of blocks that have, changed via C.O.W.? Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii" To: LVM general discussion and development Cc: Mark Woodward , Linda Walsh -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 10/04/2012 11:17 AM, Mark Woodward wrote: > I was going to try to answer in line, but decided that it would be > too much work. There are utilities to extract the exception table > out of the LVM2 snapshot, and if you can code in almost any > language, you can write your own. It is dead simple. You can google > for ddsnap and zumastore to ddsnap was the Zumastor snapshot tool which uses a different in-kernel snapshot target and metadata format. It does not share code with current (or historic afaik) LVM2/device-mapper and has been dead for a number of years (last commits around 2008). > get the code. It old and not supported currently, but still works. > I Really? I'd be surprised if it even builds against modern kernels or device-mapper. > The format of the array is simple: old_address (The offset in the > volume) followed by the new_address (the offset in the COW device). > An array of all the "old_address" values is the changed block list. > You don't even need to worry about the data if you can really get a > file list by blocks. If you really want to poke into the CoW store format I'd start by reading dm-snap-persistent.c which is the traditional device-mapper snapshot format. Snapshots using the thinp target use the metadata format described in dm-thin-metadata.c. Regards, Bryn. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAlBtoLQACgkQ6YSQoMYUY95MgACdFnOXbJC03HjQA8/p8kKxXeLD ALMAmQFhD+OfKiA2YV9RS3kaUGFzvzE0 =wsdZ -----END PGP SIGNATURE-----