KB2521 - What happens when log synchronization is enabled or disabled in an PCS / PPS cluster?

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Information

Last Modified Date	7/31/2015 5:05 PM

Synopsis

This article provides information about the behavior of a PCS / PPS cluster, when log synchronization is enabled or disabled.

Problem or Goal

When log synchronization is enabled/disabled in an PCS / PPS cluster, the following behavior is observed:

Sync enabled: Syslog server shows messages only from the Passive PCS / PPS.
Sync disabled: Syslog server shows messages from the Active and Passive PCS / PPS.

The following queries arise:

Cause

Solution

If log sync is enabled, only the cluster leader (not necessarily the active node) will send messages to the syslog server. The non-leader will send its messages to the leader, which ensures that all messages end up at the syslog server.
If sync is disabled, both nodes will independently send their messages to the syslog server.
Cluster members use a number of heuristics to select the cluster leader. The goal is to attempt to designate a node, which is expected to have the most recent state about the cluster as the leader.
For the PCS/PPS Administrator, the easiest way to determine which PCS/PPS is the cluster leader is to go to System > Clustering > Status page and hove the mouse pointer over the bullets under the Status column.

By doing this, the system will show a hexadecimal number for each bullet. The node that has the 0x08000 bit on is the leader. There will be only one node with this bit turned ON; for example, 0x18004.