[Pacemaker] How to make a redundant structure of arbitrator?

[Jiaju Zhang]

On Tue, 2012-03-27 at 12:22 +0900, Yuichi SEINO wrote:
> Hi Jiaju,
> 
> Thank you for a reply. I understand the case that a arbitrator have to
> be redundant .
> And I want to ask two questions .
> 
> 1. I think about a satisfied way. Its way is that we make a special
> site of arbitrator.
>     Can this way satisfy?
>     For example, if a running arbitrator node is stop,  this node is
> fail-over to a other node.

Ok, no problem. If the boothd on the original arbitrator node fails, it
can be started on another node to be functional, or just restarted on
the original node to proceed, but please ensure that the IP address will
be floating with the boothd as well. So, in this scenario, it seems that
you have two machines on the 3rd site to be as an arbitrator, you may
want to configure boothd as a primitive resource and let pacemaker
manage it. 
If you have 3 machines on the 3rd site, you can also configure the 3
machines as 3 different arbitrators.
If you have 3 different sites (besides that 2 cluster sites) to put one
machine each to be as arbitrator, it'll also be OK. 

If the running arbitrator node is stop, the ticket won't be failed over
from one site to the other if that two sites and the connection between
them are fine. However, the danger is: if the arbitrator is down for
quite a long time, just at that moment, one site is down or the network
connection between them is broken, the other site won't be able to get
the ticket.  
 
> 
> 2. In the case " for example, you have 2 sites, and configure 3 arbitrators",
>     if 1 arbitrators stop, the structure is 2 site and 2 arbitrators.
>     In this case, because the number of instance is an even number,
>     i think that the arbitrator can't stop anymore.
>     Am I correct　think?

Site itself is kind of arbitrator as well. So, if you have 2 sites and 3
arbitrators, totally is 5. We allow that 2 of 5 can be down to make the
booth work. Of course, the 2 should be two arbitrators or one site plus
one arbitrator. If the failed 2 are two sites, booth doesn't work;)

Thanks,
Jiaju