From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx13.extmail.prod.ext.phx2.redhat.com [10.5.110.18]) by int-mx02.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id q94F7WFf002828 for ; Thu, 4 Oct 2012 11:07:32 -0400 Received: from qmta10.emeryville.ca.mail.comcast.net (qmta10.emeryville.ca.mail.comcast.net [76.96.30.17]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q94F7V8b024046 for ; Thu, 4 Oct 2012 11:07:31 -0400 Message-ID: <506DA504.8010509@mohawksoft.com> Date: Thu, 04 Oct 2012 11:02:28 -0400 From: Mark Woodward 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> <506DA0B4.5020208@redhat.com> In-Reply-To: <506DA0B4.5020208@redhat.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"; format="flowed" To: "Bryn M. Reeves" Cc: Linda Walsh , LVM general discussion and development On 10/04/2012 10:44 AM, Bryn M. Reeves wrote: > -----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. Well..... The LVM2 code that ships with most distros still uses the old interfaces and still (Ubuntu 12.04) seemst to create a COW file with SnAp > >> 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. Where are these files to be found? > > 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-----