The following are switchover scenarios.
Node reboot — Because the main copy of the stats is maintained on both nodes, the stats are recovered from the remaining node.
Split brain — A split brain scenario should never occur. If it does, the statistics are reported from both nodes (both in SRRP master state). After the MCS recovers, the statistics are re-synchronized at the regular MCS intervals.
The active node accepts updates received from the other node only when the value of the counter is larger than the local total.
SRRP switchovers— If a host is installed by MCS, and a SRRP switchover occurs before the statistics are retrieved from the active node, the RADIUS accounting messages going out before the statistics are retrieved have unsynced statistics (statistics on a time the node did not yet receive an answer from its peer and is still requesting statistics).
After retrieving the stats, retrieved and unsynced counter values are compared and the higher counter value is chosen for accounting.