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Date: Tue, 19 Oct 2010 14:58:53 +0200
From: Dor Laor <dlaor@redhat.com>
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Subject: Re: [Qemu-devel] Re: KVM call agenda for Oct 19
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To: Avi Kivity <avi@redhat.com>
Cc: chrisw@redhat.com, kvm@vger.kernel.org, Juan Quintela <quintela@redhat.com>, qemu-devel@nongnu.org, Chris Wright <chrisw@sous-sol.org>, Ayal Baron <abaron@redhat.com>, "Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>

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. What about FS that span over LVM with multiple drives? IDE/SCSI?