From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: change tracking with block-level granularity using md Date: Wed, 18 Dec 2013 09:35:45 +0100 Message-ID: <52B15E61.4090807@suse.de> References: Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: 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: Thomas Knauth Cc: device-mapper development List-Id: dm-devel.ids On 12/18/2013 09:04 AM, Thomas Knauth wrote: > Hello list, > = > I am the author of the following paper > = > https://www.usenix.org/conference/lisa13/technical-sessions/papers/knauth > = > just presented at LISA 2013. Folks at the conference expressed > interested in seeing this merged into the official Linux kernel. I > would like to gauge your opinion of whether this has a chance to > actually be accepted. > = Well, you just implemented an asynchronous mirror with discrete tools. Congratulations. Using bitmaps for tracking modified blocks has been a standard technique in RAID1 for ages. (look for mdadm --write-behind and drivers/md/bitmap.c. It's not actually _new_ ...) Sorry for being sarcastic. But nevertheless, your tool might actually be useful; tracking block changes could have some benefit on other areas. What you should be doing: - Rename the thing (dm-linear is taken; maybe dm-bitmap ?) - Use debugfs instead of /proc - Proper formatting And then send the code for review. Or go for the full monty and break up dm-mirror to include your bitmap code. But then you would need to come up with a way of storing your bitmap on disk. Which is where the _real_ fun starts. Cheers, Hannes -- = Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg)