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

[Jan Friesse]

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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