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Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replicat
From: |
Wen Congyang |
Subject: |
Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description |
Date: |
Thu, 23 Apr 2015 18:11:03 +0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 |
On 04/23/2015 05:55 PM, Stefan Hajnoczi wrote:
> On Wed, Apr 22, 2015 at 05:28:01PM +0800, Wen Congyang wrote:
>> On 04/22/2015 05:18 PM, Stefan Hajnoczi wrote:
>>> On Tue, Apr 21, 2015 at 05:28:01PM +0200, Paolo Bonzini wrote:
>>>> On 21/04/2015 03:25, Wen Congyang wrote:
>>>>>>> Please do not introduce "<name>+colo" block drivers. This approach is
>>>>>>> invasive and makes block replication specific to only a few block
>>>>>>> drivers, e.g. NBD or qcow2.
>>>>> NBD is used to connect to secondary qemu, so it must be used. But the
>>>>> primary
>>>>> qemu uses quorum, so the primary disk can be any format.
>>>>> The secondary disk is nbd target, and it can also be any format. The cache
>>>>> disk(active disk/hidden disk) is an empty disk, and it is created before
>>>>> run
>>>>> COLO. The cache disk format is qcow2 now. In theory, it can be ant format
>>>>> which
>>>>> supports backing file. But the driver should be updated to support colo
>>>>> mode.
>>>>>
>>>>>> A cleaner approach is a QMP command or -drive options that work for any
>>>>>> BlockDriverState.
>>>>>
>>>>> OK, I will add a new drive option to avoid use "<name>+colo".
>>>>
>>>> Actually I liked the "foo+colo" names.
>>>>
>>>> These are just internal details of the implementations and the
>>>> primary/secondary disks actually can be any format.
>>>>
>>>> Stefan, what was your worry with the +colo block drivers?
>>>
>>> Why does NBD need to know about COLO? It should be possible to use
>>> iSCSI or other protocols too.
>>
>> Hmm, if you want to use iSCSI or other protocols, you should update the
>> driver
>> to implement block replication's control interface.
>>
>> Currently, we only support nbd now.
>
> I took a quick look at the NBD patches in this series, it looks like
> they are a hacky way to make quorum dynamically reconfigurable.
>
> In other words, what you really need is a way to enable/disable a quorum
> child or even add/remove children at run-time.
>
> NBD is not the right place to implement that. Add APIs to quorum so
> COLO code can use them.
>
> Or maybe I'm misinterpreting the patches, I only took a quick look...
Hmm, if we can enable/disable or add/remove a child at run-time, it is another
choice.
Thanks
Wen Congyang
>
> Stefan
>
- [Qemu-devel] [PATCH COLO v3 00/14] Block replication for continuous checkpoints, Wen Congyang, 2015/04/03
- [Qemu-devel] [PATCH COLO v3 02/14] quorum: allow ignoring child errors, Wen Congyang, 2015/04/03
- [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Wen Congyang, 2015/04/03
- Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description, Stefan Hajnoczi, 2015/04/20
- Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description, Wen Congyang, 2015/04/20
- Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description, Paolo Bonzini, 2015/04/21
- Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description, Stefan Hajnoczi, 2015/04/22
- Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description, Wen Congyang, 2015/04/22
- Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description, Stefan Hajnoczi, 2015/04/23
- Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description,
Wen Congyang <=
- Re: [Qemu-devel] [Qemu-block] [PATCH COLO v3 01/14] docs: block replication's description, Kevin Wolf, 2015/04/22
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Paolo Bonzini, 2015/04/22
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Kevin Wolf, 2015/04/23
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Paolo Bonzini, 2015/04/23
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Wen Congyang, 2015/04/23
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Kevin Wolf, 2015/04/23
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Wen Congyang, 2015/04/23
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Paolo Bonzini, 2015/04/23
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Kevin Wolf, 2015/04/23
- Re: [Qemu-devel] [PATCH COLO v3 01/14] docs: block replication's description, Paolo Bonzini, 2015/04/23