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From: Wen Congyang <wency@cn.fujitsu.com>
Message-ID: <56EA858B.9070408@cn.fujitsu.com>
Date: Thu, 17 Mar 2016 18:23:07 +0800
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Subject: Re: [Qemu-devel] [PATCH v12 2/3] quorum: implement bdrv_add_child()
 and bdrv_del_child()
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To: Alberto Garcia <berto@igalia.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Changlong Xie <xiecl.fnst@cn.fujitsu.com>, zhanghailiang <zhang.zhanghailiang@huawei.com>, qemu block <qemu-block@nongnu.org>, Markus Armbruster <armbru@redhat.com>, Jiang Yunhong <yunhong.jiang@intel.com>, Dong Eddie <eddie.dong@intel.com>, qemu devel <qemu-devel@nongnu.org>, Max Reitz <mreitz@redhat.com>, Gonglei <arei.gonglei@huawei.com>, Stefan Hajnoczi <stefanha@redhat.com>

On 03/17/2016 06:07 PM, Alberto Garcia wrote:
> On Thu 17 Mar 2016 10:56:09 AM CET, Wen Congyang wrote:
>>> We should have the failure modes documented, and how you'll use it
>>> after failover etc Without that it's really difficult to tell if this
>>> naming is right.
>>
>> For COLO, children.0 is the real disk, children.1 is replication
>> driver.  After failure, children.1 will be removed by the user. If we
>> want to continue do COLO, we need add a new children.1 again.
> 
> What if children.0 fails ?

For COLO, reading from children.1 always fails. if children.0 fails, it
means that reading from the disk fails. The guest vm will see the I/O error.

Thanks
Wen Congyang

> 
> Berto
> 
> 
> .
>