The cluster logfile is for the cluster itself and is located under /etc/pve/.clusterlog. It mostly maintains a log of login authentication of users. The following is a snippet of our .clusterlog file:
{
"data": [
{"uid": 931, "time": 1392231446, "pri": 6, "tag": "pvedaemon", "pid": 118644, "node": "pmxvm01", "user": "root@pam", "msg": "successful auth for user 'root@pam'"},
{"uid": 930, "time": 1392230545, "pri": 6, "tag": "pvedaemon", "pid": 115769, "node": "pmxvm01", "user": "root@pam", " msg": "successful auth for user 'root@pam'"},
{"uid": 929, "time": 1392229645, "pri": 6, "tag": "pvedaemon", "pid": 115769, "node": "pmxvm01", "user": "root@pam", " msg": "successful auth for user 'root@pam'"},
. . . .
. . . .