From mboxrd@z Thu Jan  1 00:00:00 1970
From: Felix Leimbach <felix.leimbach@gmail.com>
Subject: Block live migration without pausing VM
Date: Sun, 23 Sep 2012 17:03:29 +0200
Message-ID: <505F24C1.30201@gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
To: kvm@vger.kernel.org
Return-path: <kvm-owner@vger.kernel.org>
Received: from mail-bk0-f46.google.com ([209.85.214.46]:54462 "EHLO
	mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753409Ab2IWPDd (ORCPT <rfc822;kvm@vger.kernel.org>);
	Sun, 23 Sep 2012 11:03:33 -0400
Received: by bkcjk13 with SMTP id jk13so476186bkc.19
        for <kvm@vger.kernel.org>; Sun, 23 Sep 2012 08:03:32 -0700 (PDT)
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

Hi all,

I want to implement live-migration of a highly available VM but I cannot 
use shared storage.
The -b option to the migrate command already allows for copying the 
block device (locally stored raw file) and that is exactly what I want.
This worked in my experiments but the VM is unreachable (CPU halted?) 
while the block device is copied, which is unacceptable for my use-case.

Is there a way to copy the block device while the VM is running (copy on 
read or such)?
The LiveBlockMigration page in the qemu wiki [1] mentions that some of 
this is already implemented, but I cannot find any of it in the latest 
qemu-kvm.
Any pointers?

Thanks for your suggestions.

[1] http://wiki.qemu.org/Features/LiveBlockMigration