Is the ClearPass session log replicated across the cluster(between the nodes)?
No, the ClearPass session log data is maintained per node/server and will not be replicated across the cluster. Only the server configuration data is replicated across the cluster.
You might lose the session log data when you rejoin any node to the cluster or after the server upgrade. The session log data alone can be restored in the ClearPass server from the existing backup, if required.
Note: Ensure the "CPPM session log data" is included when you take the backup. And restoring the session log alone in the server that is part of a cluster will not affect the cluster sync.
ClearPass session log alone can be restored as shown below.