[Linux-HA] Redundant Rings "Still Not There?"

Robinson, Eric eric.robinson at psmnv.com
Sun Oct 24 09:10:58 MDT 2010

>> That way, if something happens to switched network #1, 
>> Corosync can still track node status through switched 
>> net #2.
>> Once this configuration is built, I can use Pacemaker 
>> with resource constraints to ensure that resource R1 
>> can only run on SERVER_A or SERVER_C (usually A) and 
>> resource R2 can only run on SERVER_B and SERVER_C (usually 
>> C) and SERVER_C acts as a failover for both resources.

> That's correct. And since it's a 3 node cluster you 
> can make this using simple constraints like this:

> location R1-prefers-A R1 100: SERVER_A
> location R1-not-B -inf: SERVER_B
> location R2-prefers-B R2 100: SERVER_B
> location R2-not-A -inf: SERVER_A

Excellent, it feels good to have finally wrapped my head around this. 

But now could someone please elaborate on Dejan Muhamedagic's original
comment that started the thread? What does "redundant rings are still
not there" mean? Is a three-node cluster an unreliable setup because
Corosync and/or Pacemaker are not really ready for that?

Eric Robinson

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