From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Thornber Subject: Re: change tracking with block-level granularity using md Date: Fri, 20 Dec 2013 16:35:06 +0000 Message-ID: <20131220163505.GA15982@debian> References: Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids On Wed, Dec 18, 2013 at 09:04:17AM +0100, Thomas Knauth wrote: > Hello list, > > I am the author of the following paper > > https://www.usenix.org/conference/lisa13/technical-sessions/papers/knauth I've been working on a similar problem. There's a new target called dm-era taking shape here: https://github.com/jthornber/linux-2.6/blob/era/drivers/md/dm-era-target.c It uses bloom filters to track changed blocks. Userland tools will access snapshots of the metadata via a metadata snapshot. I expect to post the finished code to dm-devel some time in Jan. More information about what I'm trying to do can be found here: http://device-mapper.org/blog/2013/11/12/retaining-cache-coherency-with-external-snapshots/ BTW: If you're using dm-thin your backup scenario is trivial. Just take a snapshot of the volumes you want to back up. Take a metadata snap. Examine the metadata to see which blocks have changed since you last backed up. Copy data. All you need is already written. - Joe