[ClusterLabs] Default Behavior

[Ken Gaillot]

On 06/28/2016 10:53 AM, Pavlov, Vladimir wrote:
> Hello!
> 
> We have Pacemaker cluster of two node Active/Backup (OS Centos 6.7),
> with resources IPaddr2 and ldirectord.
> 
> Cluster Properties:
> 
> cluster-infrastructure: cman
> 
> dc-version: 1.1.11-97629de
> 
> no-quorum-policy: ignore
> 
> stonith-enabled: false
> 
> The cluster has been configured for this documentation:
> http://clusterlabs.org/quickstart-redhat-6.html
> 
> Recently, there was a communication failure between cluster nodes and
> the behavior was like this:
> 
> -        During a network failure, each server has become the Master.
> 
> -        After the restoration of the network, one node killing services
> of Pacemaker on the second node.
> 
> -        The second node was not available for the cluster, but all
> resources remain active (Ldirectord,ipvs,ip address). That is, both
> nodes continue to be active.
> 
> We decided to create a test stand and play the situation, but with
> current version of Pacemaker in CentOS repos, сluster behaves differently:
> 
> -        During a network failure, each server has become the Master.
> 
> -        After the restoration of the network, all resources are stopped.
> 
> -        Then the resources are run only on one node. - This behavior
> seems to be more logical.
> 
> Current Cluster Properties on test stand:
> 
> cluster-infrastructure: cman
> 
> dc-version: 1.1.14-8.el6-70404b0
> 
> have-watchdog: false
> 
> no-quorum-policy: ignore
> 
> stonith-enabled: false
> 
> Changed the behavior of the cluster in the new version or accident is
> not fully emulated?

If I understand your description correctly, the situation was not
identical. The difference I see is that, in the original case, the
second node is not responding to the cluster even after the network is
restored. Thus, the cluster cannot communicate to carry out the behavior
observed in the test situation.

Fencing (stonith) is the cluster's only recovery mechanism in such a
case. When the network splits, or a node becomes unresponsive, it can
only safely recover resources if it can ensure the other node is powered
off. Pacemaker supports both physical fencing devices such as an
intelligent power switch, and hardware watchdog devices for self-fencing
using sbd.

> Thank you.
> 
>  
> 
>  
> 
> Kind regards,
> 
>  
> 
> *Vladimir Pavlov*