Cisco Systems Cisco Unity Connection Split Brain Recovery and Its Implications

Chapter 4 Configuring Cisco Unity 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 Connection Administration), 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.

Install, Upgrade, and Maintenance Guide for Cisco Unity Connection Release 10.x

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