[ClusterLabs] Booth ticket multi-site and quorum /Pacemaker

[Jan Friesse]

On 24/02/2022 10:28, Viet Nguyen wrote:
> Hi,
> 
> Thank you so so much for your help. May i ask a following up question:
> 
> For the option of having one big cluster with 4 nodes without booth, then,
> if one site (having 2 nodes) is down, then the other site does not work as
> it does not have quorum, am I right? Even if we have a quorum voter in

Yup, you are right

> either site A or B, then, if the site with quorum down, then, the other
> site does not work.  So, how can we avoid this situation as I want
> that if one site is down, the other site still services?

probably only with qnetd - so basically yet again site C.

Regards,
   Honza

> 
> Regards,
> Viet
> 
> On Wed, 23 Feb 2022 at 17:08, Jan Friesse <jfriesse at redhat.com> wrote:
> 
>> Viet,
>>
>> On 22/02/2022 22:37, Viet Nguyen wrote:
>>> Hi,
>>>
>>> Could you please help me out with this question?
>>>
>>> I have 4 nodes cluster running in the same network but in 2 different
>> sites
>>> (building A - 2 nodes and building B - 2 nodes). My objective is to
>>> setup HA for this cluster with pacemaker. The expectation is if a site is
>>> down, the other site still services.
>>>
>>>   From what I could understand so far, in order to make it work, it needs
>> to
>>> have booth ticket manager installed in a different location, let's say
>>> building C which connects to both sites A and B.
>>>
>>> With this assumption, i would like to ask few questions:
>>>
>>>      1. Am i right that I need to setup the booth ticket manager as a
>> quorum
>>>      voter as well?
>>
>> Yes, booth (arbitrator) has to be installed on "site" C if you want to
>> use booth. Just keep in mind booth has nothing to do with quorum.
>>
>>>      2. What happens if  the connection between site A and B is down, but
>> the
>>>      connection between A and C, B and C still up? In this case, both
>> site A and
>>>      B still have the quorum as it can connect to C, but not between each
>> other?
>>
>> If you use booth then it's not required site A to see site B. It's then
>> "site" C problem to decide which site gets ticket.
>>
>>
>>>      3. Or is there any better way to manage 2 sites cluster, each has 2
>>>      nodes? And if one site is down like environmental disaster, then,
>> the other
>>>      site still services.
>>
>> Basically there are (at least) two possible solutions:
>> - Have one big cluster without booth and use pcmk constraints
>> - Have two 2 node clusters and use booth. Then each of the two node
>> clusters is "independent" (have its own quorum) and each of the cluster
>> runs booth (site) as a cluster resource + "site" C running booth
>> (arbitrator)
>>
>> Regards,
>>     Honza
>>
>>>
>>>
>>> Thank you so much for your help!
>>> Regards,
>>> Viet
>>>
>>>
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>>
>>
>