Heartbeats

Heartbeats

In the cluster, heartbeats perform the following roles:

• To continually monitor the other nodes in the cluster, ensuring they are active and available.
• Communicate cluster and service status to the other nodes in the cluster. Status information includes mode and state for every service on that node (manual/automatic running/stopped etc), along with any services that are currently blocked.
• A checksum of the active cluster configuration on that node.

The cluster supports two types of heartbeats:

• Network heartbeats
• Disk heartbeats

Heartbeats are unidirectional therefore for each heartbeat configured there will be two channels (one to send and one to receive).

The same information and structures is transmitted over each type of heartbeat. The cluster supports multiple heartbeats of each type. When the cluster is first created a network hearbeat is automatically configured between cluster nodes using the node hostnames as the endpoints. Disk heartbeats are automatically configured when a service is created and under normal circumstances require no user intervention.

It is recommended practice to configure network heartbeats across any additional network interfaces. For example, if the hostnames are on a 10.x.x.x network, and an additional private network exists with 192.x.x.x addresses, then an additional heartbeat can be configured on that private network. Using the following example hosts file an additional network heartbeat can be configured using the node-a-priv and node-b-priv addresses as endpoints:

10.0.0.1 node-a
10.0.0.2 node-b
192.168.72.1 node-a-priv
192.168.72.2 node-b-priv

By specifying the endpoint using the address of an additional interface the cluster will automatically route heartbeat packets down the correct network for that interface.

To view the cluster heartbeats navigate to HA-Cluster -> Heartbeats on the left side-menu:

Adding a Network Heartbeat

To add an additional network heartbeat to the cluster, select Add Network Heartbeat Pair. In this example an additional physical network connection exists between the two nodes. The end points for this additional network are given the names SAM node-a-priv and node-b-priv respectively. These hostnames are then used when configuring the additional heartbeat:

Click Submit to add the heartbeat. The new heartbeat will now be displayed on the Heartbeats status page:

Removing a Network Heartbeat

To remove a network heartbeat select the heartbeat using the slider on the left hand side of the table and click the remove selected button:

Finally, confirm the action:

Disk heartbeats

Under normal circumstances it should not be necessary to add or remove disk heartbeats as this is handled automatically by the cluster.