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Re: [Qemu-devel] [PATCH v9 2/3] quorum: implement bdrv_add_child() and b
From: |
Alberto Garcia |
Subject: |
Re: [Qemu-devel] [PATCH v9 2/3] quorum: implement bdrv_add_child() and bdrv_del_child() |
Date: |
Thu, 21 Jan 2016 14:05:23 +0100 |
User-agent: |
Notmuch/0.13.2 (http://notmuchmail.org) Emacs/23.2.1 (i486-pc-linux-gnu) |
On Thu 21 Jan 2016 02:54:10 AM CET, Wen Congyang <address@hidden> wrote:
>>> @@ -875,9 +878,9 @@ static int quorum_open(BlockDriverState *bs, QDict
>>> *options, int flags,
>>> ret = -EINVAL;
>>> goto exit;
>>> }
>>> - if (s->num_children < 2) {
>>> + if (s->num_children < 1) {
>>> error_setg(&local_err,
>>> - "Number of provided children must be greater than 1");
>>> + "Number of provided children must be 1 or more");
>>> ret = -EINVAL;
>>> goto exit;
>>> }
>>
>> I have a question: if you have a Quorum with just one member and you
>> add a new one, how do you know if it has the same data as the
>> existing one?
>>
>> 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?
Berto