From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] Re: KVM call agenda for Oct 19 Date: Tue, 19 Oct 2010 08:18:04 -0500 Message-ID: <4CBD9A8C.202@codemonkey.ws> References: <20101019021117.GI25455@sequoia.sous-sol.org> <4CBD93B8.9070002@redhat.com> <4CBD955E.8060909@redhat.com> <4CBD960D.8020806@redhat.com> <4CBD9736.2060902@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: dlaor@redhat.com, Chris Wright , Juan Quintela , chrisw@redhat.com, "Venkateswararao Jujjuri (JV)" , qemu-devel@nongnu.org, kvm@vger.kernel.org, Ayal Baron , Michael D Roth To: Avi Kivity Return-path: Received: from mail-vw0-f46.google.com ([209.85.212.46]:46850 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758001Ab0JSNSK (ORCPT ); Tue, 19 Oct 2010 09:18:10 -0400 Received: by vws2 with SMTP id 2so1368861vws.19 for ; Tue, 19 Oct 2010 06:18:10 -0700 (PDT) In-Reply-To: <4CBD9736.2060902@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 10/19/2010 08:03 AM, Avi Kivity wrote: > On 10/19/2010 02:58 PM, Dor Laor wrote: >> On 10/19/2010 02:55 PM, Avi Kivity wrote: >>> On 10/19/2010 02:48 PM, Dor Laor wrote: >>>> On 10/19/2010 04:11 AM, Chris Wright wrote: >>>>> * Juan Quintela (quintela@redhat.com) wrote: >>>>>> >>>>>> Please send in any agenda items you are interested in covering. >>>>> >>>>> - 0.13.X -stable handoff >>>>> - 0.14 planning >>>>> - threadlet work >>>>> - virtfs proposals >>>>> >>>> >>>> - Live snapshots >>>> - We were asked to add this feature for external qcow2 >>>> images. Will simple approach of fsync + tracking each requested >>>> backing file (it can be per vDisk) and re-open the new image would >>>> be accepted? >>>> - Integration with FS freeze for consistent guest app snapshot >>>> Many apps do not sync their ram state to disk correctly or frequent >>>> enough. Physical world backup software calls fs freeze on xfs and >>>> VSS for windows to make the backup consistent. >>>> In order to integrated this with live snapshots we need a guest >>>> agent to trigger the guest fs freeze. >>>> We can either have qemu communicate with the agent directly through >>>> virtio-serial or have a mgmt daemon use virtio-serial to >>>> communicate with the guest in addition to QMP messages about the >>>> live snapshot state. >>>> Preferences? The first solution complicates qemu while the second >>>> complicates mgmt. >>> >>> Third option, make the freeze path management -> qemu -> virtio-blk -> >>> guest kernel -> file systems. The advantage is that it's easy to >>> associate file systems with a block device this way. >> >> OTH the userspace freeze path already exist and now you create >> another path. > > I guess we would still have a userspace daemon; instead of talking to > virtio-serial it talks to virtio-blk. So: > > management -> qemu -> virtio-blk -> guest driver -> kernel fs > resolver -> daemon -> apps > > Yuck. Yeah, in Windows, I'm pretty sure the freeze API is a userspace concept. Various apps can hook into it to serialize their state. At the risk of stealing Mike's thunder, we've actually been working on a simple guest agent exactly for this type of task. Mike's planning an RFC for later this week but for those that are interested the repo is at http://repo.or.cz/w/qemu/mdroth.git Regards, Anthony Liguori > >> What about FS that span over LVM with multiple drives? IDE/SCSI? > > Good points. >