The Unity Connection cluster feature provides
high availability voice messaging through two Unity Connection servers that are
configured in a cluster.
The Unity Connection cluster behavior when both the servers are
The cluster can be assigned a DNS name that is shared by the
Unity Connection servers.
Clients, such as email applications and the web tools available
through the Cisco Personal Communications Assistant (PCA) can connect to either
of the Unity Connection server.
Phone systems can send calls to either of the Unity Connection
Incoming phone traffic load is balanced between the Unity
Connection servers by the phone system, PIMG/TIMG units, or other gateways that
are required for the phone system integration.
Each server in a cluster is responsible for handling a
share of the incoming calls for the cluster (answering phone calls and taking
messages). The server with Primary status is responsible for the following
Homing and publishing the database and message store that are
replicated to the other server.
Sending message notifications and MWI requests (the Connection
Notifier service is activated).
Sending SMTP notifications and VPIM messages (the Connection
Message Transfer Agent service is activated).
Synchronizing voice messages between Unity Connection and
Exchange mailboxes, if the unified messaging feature is configured (the Unity
Connection Mailbox Sync service is activated).
When one of the servers stops functioning (for example, when it
is shutdown for maintenance), the remaining server resumes the responsibility
of handling all the incoming calls for the cluster. The database and message
store are replicated to the other server when its functionality is restored.
When the server that stopped functioning is able to resume its
normal functions and is activated, it resumes responsibility of handling its
share of incoming calls for the cluster.
It is recommended to perform provisioning only on the Publisher
server in Active-Active mode and on Subscriber (Acting Primary) in case of
cluster failover. The password change and password setting modification for
User PIN/Web application should be provisioned on Publisher server in
To monitor the server status, the Connection
Server Role Manager service runs in Cisco Unity Connection Serviceability on
both the servers. This service performs the following functions:
Starts the applicable services on each server, depending on
Determines whether critical processes (such as voice message
processing, database replication, voice message synchronization with Exchange,
and message store replication) are functioning normally.
Initiates changes to server status when the server with Primary
status is not functioning or when critical services are not running.
Note the following limitations when the publisher server is not
If the Unity Connection cluster is integrated with an LDAP
directory, directory synchronization does not occur, although authentication
continues to work when only the subscriber server is functioning. When the
publisher server is resumes functioning, directory synchronization also
If a digital or HTTPS network includes the Unity Connection
cluster, directory updates do not occur, although messages continue to be sent
to and from the cluster when only the subscriber server is functioning. When
the publisher server is functioning again, directory updates resume.
The Connection Server Role Manager service sends a keep-alive
events between the publisher and subscriber servers to confirm that the servers
are functioning and connected. If one of the servers stops functioning or the
connection between the servers is lost, the Connection Server Role Manager
service waits for the keep-alive events and may require 30 to 60 seconds to
detect that the other server is not available. While the Connection Server Role
Manager service is waiting for the keep-alive events, users signing in to the
server with Secondary status are not 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.
It is recommended to import and delete the LDAP users from the
publisher node only.