From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:59715) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Sw8q3-0004Zz-EG for qemu-devel@nongnu.org; Tue, 31 Jul 2012 05:34:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Sw8px-0004bX-G2 for qemu-devel@nongnu.org; Tue, 31 Jul 2012 05:34:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:4245) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Sw8px-0004bL-6M for qemu-devel@nongnu.org; Tue, 31 Jul 2012 05:33:57 -0400 Message-ID: <5017A680.8050305@redhat.com> Date: Tue, 31 Jul 2012 11:33:52 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1343127865-16608-1-git-send-email-pbonzini@redhat.com> <1343127865-16608-29-git-send-email-pbonzini@redhat.com> <5017A4DA.80602@redhat.com> In-Reply-To: <5017A4DA.80602@redhat.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 28/47] qmp: add drive-mirror command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: jcody@redhat.com, eblake@redhat.com, qemu-devel@nongnu.org, stefanha@linux.vnet.ibm.com Il 31/07/2012 11:26, Kevin Wolf ha scritto: > Am 24.07.2012 13:04, schrieb Paolo Bonzini: >> This adds the monitor commands that start the mirroring job. >> >> Signed-off-by: Paolo Bonzini > > [ Moving the discussion upstream ] > >> Why make all of it inaccessible? Everything except target device access >> does have a stable API. The target device access can be delayed to 1.3, >> together with the much-needed QMP schema introspection. > > I'm not even sure about the QMP mirror command itself. > > I don't really like it, it does too many things at once: It can create > the target image file, it opens the target and it actually starts the > mirroring. It's rather bad at the first two steps, because it doesn't > take any options. This means that it can't create qcow2v3 images, for > example. Or you can't mirror into a backup with cache=unsafe while > running your real VM on cache=writethrough. Yes, though this can be worked around with mode: 'existing'. > Having an all-in-one mirror command is a nice feature for HMP, but for > QMP it's more like a design problem. > > Now I see you have called it drive-mirror I thought this was your idea. :) > , so that kind of implies that > it's not the final blockdev-mirror but just a QMP version of a command > primarily designed for HMP. As such this restricted functionality may be > acceptable, but it's not like everything is already perfect and there's > no room for discussion. We keep going back to the same point that we do not have -blockdev, but it's becoming a bit frustrating to always rehash this same point... Paolo