From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:58703) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TsBv3-0001UJ-Jj for qemu-devel@nongnu.org; Mon, 07 Jan 2013 07:35:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TsBv2-0008W0-Cf for qemu-devel@nongnu.org; Mon, 07 Jan 2013 07:35:09 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:54554) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TsBv2-0008VT-6Z for qemu-devel@nongnu.org; Mon, 07 Jan 2013 07:35:08 -0500 Received: by mail-bk0-f46.google.com with SMTP id q16so8481914bkw.33 for ; Mon, 07 Jan 2013 04:35:07 -0800 (PST) Date: Mon, 7 Jan 2013 13:35:04 +0100 From: Stefan Hajnoczi Message-ID: <20130107123504.GB17997@stefanha-thinkpad.redhat.com> References: <50D2CC22.1060900@linux.vnet.ibm.com> <50D3C8AF.7050506@linux.vnet.ibm.com> <20130104173550.GB9481@stefanha-thinkpad.redhat.com> <87623ca7up.fsf@elfo.mitica> <50E7E27A.8050209@linux.vnet.ibm.com> <50E8EF52.5080507@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50E8EF52.5080507@redhat.com> Subject: Re: [Qemu-devel] [RFC] lively write vmstate with predictable size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Anthony Liguori , Pavel Hrdina , quintela@redhat.com, qemu-devel , Dietmar Maurer , Paolo Bonzini , Wenchao Xia On Sat, Jan 05, 2013 at 08:28:18PM -0700, Eric Blake wrote: > On 01/05/2013 01:21 AM, Wenchao Xia wrote: > > I guess migration to file makes vm stopped, and lack a step > > to take snapshot in the end of migration, also the usage seems > > strange makes me feel something is lacking. I'd like to > > have: > > 1 take blk snapshot internal/external lively. > > 2 take vmstate snapshot internal/external lively. > > 3 combination. > > Libvirt 1.0.1 can already do external live snapshots - it does a live > migration to file, and when that finally converges enough to pause, > there is less than a second of downtime when libvirt then follows up > with an external disk snapshot and then resumes the guest. Of course, > this approach requires multiple files, and there is no way to take an > internal snapshot with current QMP support. And the point remains in > this thread that a live migration to file takes more space than a paused > migration, in part because earlier portions of the migration stream are > revisited later in the stream as memory pages continue to be touched > during the live migration. So a new format for seekable migration to > file, different than current migration being usable over a fifo, may > indeed allow for less disk space and faster booting when reverting to > that vmstate. Thanks for the explanations Wenchao, Juan, and Eric. Stefan