From: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
To: Alberto Garcia <berto@igalia.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu block <qemu-block@nongnu.org>,
Jiang Yunhong <yunhong.jiang@intel.com>,
Dong Eddie <eddie.dong@intel.com>,
qemu devel <qemu-devel@nongnu.org>,
Markus Armbruster <armbru@redhat.com>,
Gonglei <arei.gonglei@huawei.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
zhanghailiang <zhang.zhanghailiang@huawei.com>
Subject: Re: [Qemu-devel] [PATCH v9 2/3] quorum: implement bdrv_add_child() and bdrv_del_child()
Date: Tue, 16 Feb 2016 14:05:07 +0800 [thread overview]
Message-ID: <56C2BC13.7020906@cn.fujitsu.com> (raw)
In-Reply-To: <w5137t39lnb.fsf@maestria.local.igalia.com>
On 02/09/2016 01:06 AM, Alberto Garcia wrote:
> On Fri 22 Jan 2016 09:02:10 PM CET, "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
>
>>>>>>> In general, what do you do to make sure that the data in a new
>>>>>>> Quorum child is consistent with that of the rest of the array?
>>>>>>
>>>>>> Quorum can have more than one child when it starts. But we don't
>>>>>> do the similar check. So I don't think we should do such check
>>>>>> here.
>>>>>
>>>>> Yes, but when you start a VM you can verify in advance that all
>>>>> members of the Quorum have the same data. If you do that on a
>>>>> running VM how can you know if the new disk is consistent with the
>>>>> others?
>>>>
>>>> User error if it is not. Just the same as it is user error if you
>>>> request a shallow drive-mirror but the destination is not the same
>>>> contents as the backing file. I don't think qemu has to protect us
>>>> from user error in this case.
>>>
>>> But the backing file is read-only so the user can guarantee that the
>>> destination has the same data before the shallow mirror. How do you
>>> do that in this case?
>>
>> I think in the colo case they're relying on doing a block migrate to
>> synchronise the remote disk prior to switching into colo mode.
>
> Yes but this is a general API that can be used independently from
> COLO. I'd say if we want to allow that we should at least place a big
> warning in the documentation.
>
Ok, that's fair enough. Will add in next version.
Thanks
-Xie
> Berto
>
>
> .
>
next prev parent reply other threads:[~2016-02-16 6:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-25 9:22 [Qemu-devel] [PATCH v9 0/3] qapi: child add/delete support Changlong Xie
2015-12-25 9:22 ` [Qemu-devel] [PATCH v9 1/3] Add new block driver interface to add/delete a BDS's child Changlong Xie
2015-12-25 9:22 ` [Qemu-devel] [PATCH v9 2/3] quorum: implement bdrv_add_child() and bdrv_del_child() Changlong Xie
2016-01-20 15:43 ` Alberto Garcia
2016-01-21 1:54 ` Wen Congyang
2016-01-21 13:05 ` Alberto Garcia
2016-01-21 16:58 ` Eric Blake
2016-01-22 9:42 ` Alberto Garcia
2016-01-22 20:02 ` Dr. David Alan Gilbert
2016-01-25 1:13 ` Wen Congyang
2016-02-08 17:06 ` Alberto Garcia
2016-02-16 6:05 ` Changlong Xie [this message]
2015-12-25 9:22 ` [Qemu-devel] [PATCH v9 3/3] qmp: add monitor command to add/remove a child Changlong Xie
2016-02-10 18:02 ` [Qemu-devel] [Qemu-block] " Max Reitz
2016-02-15 5:01 ` Changlong Xie
2016-01-18 1:17 ` [Qemu-devel] [PATCH v9 0/3] qapi: child add/delete support Wen Congyang
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