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Install, Upgrade, and Maintenance Guide for Cisco Unity Connection Release 10.x
Chapter4 Configuring CiscoUnity Connection Cluster
Understanding Cluster in Detail
available. While the Connection Server Role Manager service is waiting for the keep-alive events,
users signing in to the server with Secondary status will not be able to access their mailbox or send
messages, because the Connection Server Role Manager service has not yet detected that the server
with Primary status (which has the active message store) is unavailable. In this situation, callers who
attempt to leave a message may hear dead air or may not hear the recording beep.
Note It is recommended to import and delete the LDAP users from the publisher node only.
Effects of Split Brain Condition in a Unity Connection Cluster
When both the servers in a Unity Connection cluster have Primary status at the same time (for example,
when the servers have lost their connection with each other), both servers handle the incoming calls
(answer phone calls and take messages), send message notifications, send MWI requests, accept changes
to the administrative interfaces (such as Unity ConnectionAdministration), and synchronize voice
messages in Unity Connection and Exchange mailboxes if single inbox is turned on. However, the
servers do not replicate the database and message store to each other and do not receive replicated data
from each other.
When the connection between the servers is restored, the status of the servers temporarily changes to
Split Brain Recovery while the data is replicated between the servers and MWI settings are coordinated.
During the time when the server status is Split Brain Recovery, the Connection Message Transfer
Agent service and the Connection Notifier service (in Cisco Unity Connection Serviceability) are
stopped on both servers, so Unity Connection does not deliver any messages and does not send any
message notifications. The Connection Mailbox Sync service is also stopped, so Unity Connection does
not synchronize voice messages with Exchange (single inbox). The message stores are also briefly
dismounted, so that Unity Connection tells users who are trying to retrieve their messages at this point
that their mailboxes are temporarily unavailable.
When the recovery process is complete, the Connection Message Transfer Agent service and the
Connection Notifier service are started on the publisher server. Delivery of the messages that arrived
while during the recovery process may take additional time, depending on the number of messages to be
delivered. The Connection Message Transfer Agent service and the Connection Notifier service are
started on the subscriber server. Finally, the publisher server has Primary status and the subscriber server
has Secondary status. At this point, the Connection Mailbox Sync service is started on the server with
Primary status, so that Unity Connection can resume synchronizing voice messages with Exchange if
single inbox is turned on.