[Linux-ha-dev] Re: Shared disk file Exclusiveness control program for HB2

[OKADA Satoshi]

Hi, 

Thank you for your comment.
We will check the operation and source code of the quorum 
plugin from now. 

Thanks, 
OKADA Satoshi


> Hi,
>
> I agree with Alan, if this part of work goes into a quorum module, it
> would be perfect.
> Quorum module is a kind of plugin too, so it is not an internal
> behavior of heartbeat.
>
> When a split-brain happened, the side with more nodes will take the
> quorum and continue the service, the less nodes side will lost the
> quorum then be fenced.
>
> The problem is when the two sides have same number of nodes. We need a
> tie breaker in this case. The quorum plugin is going to do this.
>
> We implemented a quorum server which running out of the cluster, the
> side which is still connecting to the quorum server will get the
> quorum. if both connections are ok, the one who has connected to
> quorum server first will get the quorum.
>
> The SF-EX can be used to break the tie too. When the split brain
> happens, the side which still can access  the share disk will get the
> quorum and continue it's service. The other side will be fenced. And
> this is what we expect.
>
> And it's easy to implement a quorum plugin, the interface is in
> include/clplumbing/cl_quorum.h, and you can refer to the implements in
> lib/plugins/quorum/.
>
> On 8/9/07, Alan Robertson <alanr at unix.sh> wrote:
>   
>> OKADA Satoshi wrote:
>>     
>>> Hi Alan and all,
>>>       
>>>> Hi Alan,
>>>>
>>>> Thank you for your comment.
>>>> This program isn't considered as a quorum module for now.
>>>> It was developed as RA, I mean, it provides an independent function
>>>> without
>>>> some effects to Heartbeat's internal behavior.
>>>>
>>>> since we don't have familiar with a quorum module,
>>>> what are the requirements for it?
>>>> We have no problem with improving it, but it's not known exactly how we
>>>> should do.
>>>>         
>> I don't know exactly either, because I didn't write that code, but only
>>     
>>> For example, SF-EX accesses to disk periodically by the active node to
>>> keep holding lock.
>>> We think quorum module can not operate this. Are we wrong?
>>>       
>> The quorum server module operates in a very similar way.  It has to send
>> periodic heartbeats to the quorum server, or the quorum server would
>> take away its quorum.  So, in that sense it's very similar.  They are
>> sending packets, and you are doing disk I/O - but both have to do it
>> periodically, or it won't be able to keep quorum.
>>
>> I have CCed Huang Zhen, who added the plugin interface for the quorum
>> modules, and who also wrote the quorum daemon itself.
>>
>> I suppose I should go read the code, but I'm on traveling with my wife
>> right now, and until Monday am on holiday.
>>
>> --
>>     Alan Robertson <alanr at unix.sh>
>>
>> "Openness is the foundation and preservative of friendship...  Let me
>> claim from you at all times your undisguised opinions." - William
>> Wilberforce
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>>
>>     
>
>
>