[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-block] [PATCH v12 2/3] quorum: implement bdrv_add_child() and

From: Max Reitz
Subject: Re: [Qemu-block] [PATCH v12 2/3] quorum: implement bdrv_add_child() and bdrv_del_child()
Date: Tue, 29 Mar 2016 17:52:27 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0

On 29.03.2016 17:50, Dr. David Alan Gilbert wrote:
> * Eric Blake (address@hidden) wrote:
>> On 03/29/2016 09:38 AM, Max Reitz wrote:
>>> On 17.03.2016 10:56, Wen Congyang wrote:
>>>> On 03/17/2016 05:48 PM, Dr. David Alan Gilbert wrote:
>>> [...]
>>>>> The children.0 notation is really confusing in the way that Berto
>>>>> describes; I hit this a couple of months ago and it really doesn't
>>>>> make sense.
>>>> Do you mean: read from children.1 first, and then read from children.0 in
>>>> fifo mode? Yes, the behavior is very strange.
>>> So is this intended or is it not? In
>>> http://lists.nongnu.org/archive/html/qemu-block/2016-03/msg00526.html
>>> you said that it is.
>>> I myself would indeed say it is very strange. If I were a user, I would
>>> not expect this behavior. And as I developer, I think that how a BDS's
>>> child is used by its parent should solely depend on its role (e.g.
>>> whether it is "children.0" or "children.1").
>> It sounds like the argument here, and in Max's thread on
>> query-block-node-tree, is that we DO have cases where order matters, and
>> so we need a way for the hot-add operation to explicitly specify where
>> in the list a child is inserted (whether it is being inserted as the new
>> primary image, or explicitly as the last resort, or somewhere in the
>> middle).  An optional parameter, that defaults to appending, may be ok,
>> but we definitely need to consider how the order of children is affected
>> by hot-add.
> Certainly in the COLO case the two children are not identical; and IMHO we 
> need
> to get away from thinking about ordering and start thinking about functional
> namingd - children.0/children.1 doesn't suggest the fact they behave
> differently.

To me it does. If quorum is operating in a mode call "FIFO" I would
expect some order on the child nodes, and if the child nodes are
actually numbered in an ascending order, that is an obvious order.


Attachment: signature.asc
Description: OpenPGP digital signature

reply via email to

[Prev in Thread] Current Thread [Next in Thread]