From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:53607) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gmbIr-0004O8-Dc for qemu-devel@nongnu.org; Thu, 24 Jan 2019 04:28:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gmb82-0001dg-Ut for qemu-devel@nongnu.org; Thu, 24 Jan 2019 04:16:55 -0500 Date: Thu, 24 Jan 2019 10:16:49 +0100 From: Kashyap Chamarthy Message-ID: <20190124091649.GF23279@paraplu> References: <9aef3157-e49e-4b53-f0de-75593df06da9@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9aef3157-e49e-4b53-f0de-75593df06da9@redhat.com> Subject: Re: [Qemu-devel] Incremental drive-backup with dirty bitmaps List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Bharadwaj Rayala , qemu-devel@nongnu.org, Kashyap Chamarthy , Suman Swaroop , John Snow , qemu-discuss@nongnu.org On Wed, Jan 23, 2019 at 01:09:41PM -0600, Eric Blake wrote: > On 1/23/19 12:08 PM, Bharadwaj Rayala wrote: [...] # [Snip Eric's excellent exposition.] > > What do you mean by issues? Do you mean any data/corruption bugs or lack of > > some nice functionality that we are talking here? > > Lack of functionality. In particular, the 4.0 commands > block-dirty-bitmap-{enable,merge,disable} (or their 3.1 counterparts > x-block-dirty-bitmap-*) are essential to the workflow of differential > backups (without being able to manage bitmaps yourself, you can only get > the weaker incremental backup, and that means qemu itself is clearing > the bitmap out of under your feet on success, and where you are having > to worry about completion-mode=grouped). > > > > > Thanks a lot Eric for spending your time in answering my queries. I dont > > know if you work with Kashyap Chamarthy, but your help and his blogs are > > lifesavers. > > Yes, Kashyap is trying to build solutions on top of the building blocks > that I am working on, so we have collaborated several times on these > types of issues (he does a lot better at blog posts extracted from my > mailing list brain dumps). I haven't kept up with incremental backups lately, as I've been swamped with other work. But two other documents that I can point to are these [1][2] in the QEMU tree. And their HTML-rendered versions are here[3][4]. They're generated for 3.0.0; but these docs haven't changed much since then. Along with Eric's last year talk, also check out presentations from previous KVM Forums from other Block Layer maintainers. [1] https://git.qemu.org/?p=qemu.git;a=blob;f=docs/interop/live-block-operations.rst [2] https://git.qemu.org/?p=qemu.git;a=blob;f=docs/interop/bitmaps.rst [3] https://kashyapc.fedorapeople.org/QEMU-Docs-v3.0.0/_build/html/docs/interop/live-block-operations.html [4] https://kashyapc.fedorapeople.org/QEMU-Docs-v3.0.0/_build/html/docs/interop/bitmaps.html -- /kashyap