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Subject: Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Yang Hongyang <yanghy@cn.fujitsu.com>, Fam Zheng <famz@redhat.com>, qemu block <qemu-block@nongnu.org>, armbru@redhat.com, jcody@redhat.com, Jiang Yunhong <yunhong.jiang@intel.com>, Dong Eddie <eddie.dong@intel.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>, qemu devel <qemu-devel@nongnu.org>, zhanghailiang <zhang.zhanghailiang@huawei.com>, Gonglei <arei.gonglei@huawei.com>, Max Reitz <mreitz@redhat.com>, Lai Jiangshan <laijs@cn.fujitsu.com>


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On Fri, Apr 24, 2015 at 11:36:35AM +0200, Paolo Bonzini wrote:
>=20
>=20
> On 24/04/2015 11:38, Wen Congyang wrote:
> >> >=20
> >> > That can be done with drive-mirror.  But I think it's too early for =
that.
> > Do you mean use drive-mirror instead of quorum?
>=20
> Only before starting up a new secondary.  Basically you do a migration
> with non-shared storage, and then start the secondary in colo mode.
>=20
> But it's only for the failover case.  Quorum (or a new block/colo.c
> driver or filter) is fine for normal colo operation.

Perhaps this patch series should mirror the Secondary's disk to a Backup
Secondary so that the system can be protected very quickly after
failover.

I think anyone serious about fault tolerance would deploy a Backup
Secondary, otherwise the system cannot survive two failures unless a
human administrator is lucky/fast enough to set up a new Secondary.

Stefan

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