From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:43721) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S229j-0004Y7-Sc for qemu-devel@nongnu.org; Mon, 27 Feb 2012 10:06:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S229d-0004dW-1o for qemu-devel@nongnu.org; Mon, 27 Feb 2012 10:06:27 -0500 Received: from mail-pz0-f45.google.com ([209.85.210.45]:43055) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S229c-0004dO-Rh for qemu-devel@nongnu.org; Mon, 27 Feb 2012 10:06:20 -0500 Received: by dadp14 with SMTP id p14so6373687dad.4 for ; Mon, 27 Feb 2012 07:06:19 -0800 (PST) Message-ID: <4F4B9BE7.1010100@codemonkey.ws> Date: Mon, 27 Feb 2012 09:06:15 -0600 From: Anthony Liguori MIME-Version: 1.0 References: <20120224170143.78f55d3e@doriath.home> <8eaeb022-ea20-4823-886a-e629bce1c776@zmail16.collab.prod.int.phx2.redhat.com> <20120227091215.7849e558@doriath.home> <4F4B7BCD.6000808@redhat.com> <20120227100645.3f36d52d@doriath.home> <4F4B95A5.3000804@redhat.com> <4F4B9761.3010601@codemonkey.ws> <4F4B9931.30708@redhat.com> <4F4B9A46.3090706@codemonkey.ws> <4F4B9B54.7070700@redhat.com> In-Reply-To: <4F4B9B54.7070700@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] drive transactions (was Re: [PATCH 2/2 v2] Add the blockdev-reopen and blockdev-migrate commands) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: kwolf@redhat.com, Jeff Cody , mtosatti@redhat.com, armbru@redhat.com, qemu-devel@nongnu.org, Federico Simoncelli , Luiz Capitulino On 02/27/2012 09:03 AM, Paolo Bonzini wrote: > On 02/27/2012 03:59 PM, Anthony Liguori wrote: >> The problem is that the current commands are not designed well. For >> instance, multi-snapshot could look like: >> >> block-freeze ide0-hd0 >> block-freeze ide1-hd1 >> block-reopen ide0-hd0 my-new-file0.qcow2 >> block-reopen ide1-hd1 my-new-file1.qcow2 >> block-unfreeze ide1-hd1 >> block-unfreeze ide1-hd0 >> >> This would work regardless of whether the commands were implemented >> asynchronously within QEMU too. > > This looks good, too. Positive: maps well to fsfreeze/thaw with help > from the guest agent. Negative: you have to specify the devices three > times. Overall, I think I like it. > > However, you need to add freeze/unfreeze capabilities to the block > layer. Not hard, but one more thing to do. Right. But it also generalizes to other QMP operations which is potentially interesting. And providing mechanisms like this gives more flexibility to management tools to implement interesting features without constantly chancing new QMP commands. Regards, Anthony Liguori > > Paolo