[Pacemaker] Cluster Amnesia problem in Pacemaker

Andrew Beekhof andrew at beekhof.net
Mon Aug 2 03:51:23 EDT 2010

On Fri, Jul 30, 2010 at 2:15 PM, chajo <shakes1714 at yahoo.com> wrote:
> Hi,
>      i am a beginner in pacemaker and in the process of understanding it
> better. its usage on openais stack. while reading about cluster properties i
> came across this problem "clsuter amnesia". i am not sure this problem exists
> in Pacemaker ( i dont have setup right now to experiment this :( )
> i am aware that when a node in a Pacemaker(on openais) has its configuration
> updated locally it is synchronized on all nodes of that cluster. and read in
> Pacemaker documentation that whenever a node joins cluster asks the node with
> the highest (admin_epoch, epoch,num_updates) tuple to replace the
> configuration on all the nodes. i understood this is the case when nodes are
> online.
> cluster amnesia  is basically on a two node cluster (node A, node B), if node
> A is down and node B is up.. and on node B we add 2 new resources (make
> someother config change) and save the configuration. next we bring node B
> down. now when we start node A it comes up with old configuration ( it missed
> newly added 2 resources on node B).
> i would like to understand whether this problem exists with  with pacemaker?

Of course it does.
How is A supposed to know about the new configuration if its down when
the change is made and no-one is around when it comes up?

> or some solution already exists in Pacemaker to take care of this problem?

"Don't do that"

> i tried to search the forum with keyword "amnesia" couldn't get any results
> am going to experiment this once i get setup in two days.
> thanks in advance
> chajo
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