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Date: Tue, 30 Jun 2015 20:01:47 +0100
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Subject: Re: [Qemu-devel] [Qemu-block] [PATCH COLO-Block v6 07/16] Add new
 block driver interface to connect/disconnect the remote target
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To: Wen Congyang <wency@cn.fujitsu.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <famz@redhat.com>, Wen Congyang <ghostwcy@gmail.com>, qemu block <qemu-block@nongnu.org>, Stefan Hajnoczi <stefanha@gmail.com>, Jiang Yunhong <yunhong.jiang@intel.com>, Dong Eddie <eddie.dong@intel.com>, qemu devel <qemu-devel@nongnu.org>, Max Reitz <mreitz@redhat.com>, Lai Jiangshan <laijs@cn.fujitsu.com>, Gonglei <arei.gonglei@huawei.com>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Yang Hongyang <yanghy@cn.fujitsu.com>, zhanghailiang <zhang.zhanghailiang@huawei.com>

* Wen Congyang (wency@cn.fujitsu.com) wrote:
> On 06/27/2015 03:03 AM, Dr. David Alan Gilbert wrote:

<snip>

> > Ah, I hadn't realised you could do that; so do you just do:
> >=20
> > migrate_set_parameter colo on
> > migrate -d -b tcp:otherhhost:port
> >=20
> > How does the secondary know to feed that data straight into the disk wi=
thout
> > recording all the old data into the hidden-disk ?
>=20
> hidden disk and active disk will be made empty when starting block replic=
ation.

Hmm, yes - I think I need to update to your current world; in the version
=66rom the end of May, I get a 'error while loading state for instance 0x0 =
of device 'block''
if I try to use migrate -d -b=20
(the bdrv_write fails)

> >> If the user uses mirror job, we don't cancel the mirror job now.
> >=20
> > It would be good to get it to work with mirror, that seems preferred th=
ese
> > days to the old block migration.
>=20
> In normal migration, is mirror job created and cancelled by libvirt?

Yes, I think so; you should be able to turn on full logging on libvirt and
watch the qmp commands it sends.

Dave

--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK