cman - cluster.conf cman configuration section

Cman configuration values are placed in the <cman> </cman> section of cluster.conf. Per-node configuration related to cman is placed in the standard <clusternode> </clusternode> sections. All cman configuration settings are optional; usually none are used.

UDP port By default, cman will use UDP port 6809 for internode communication. This can be changed by setting a port number as follows:

<cman port="6809"> </cman>

Expected votes The expected votes value is used by cman to determine quorum. The cluster is quorate if the sum of votes of existing members is over half of the expected votes value. By default, cman_tool sets the expected votes value to be the sum of votes of all nodes listed in cluster.conf. This can be overriden by setting an explicit expected_votes value as follows:

<cman expected_votes="3"> </cman>

If the cluster becomes partitioned, improper use of this option can result in more than one partition gaining quorum. In that event, nodes in each partition will enable cluster services.

Two node clusters Ordinarily, the loss of quorum after one out of two nodes fails will prevent the remaining node from continuing (if both nodes have one vote.) Special configuration options can be set to allow the one remaining node to continue operating if the other fails. To do this only two nodes, each with one vote, can be defined in cluster.conf. The two_node and expected_votes values must then be set to 1 in the cman section as follows.

<cman two_node="1" expected_votes="1"> </cman>

Node votes By default, a node is given one vote toward the calculation of quorum. This can be changed by giving a node a specific number of votes as follows:

<clusternode name="nd1" votes="2"> </clusternode>

Node ID

By default, a node is assigned a nodeid by the cluster manager (cman) when it joins the cluster. This can be overriden by specifying a nodeid here. Using this option will ensure that a given node always has the same ID. A node's application to join the cluster may be rejected if you try to set the nodeid to one that is already used.

<clusternode name="nd1" nodeid="1"> </clusternode>

Multicast network configuration Cman can be configured to use multicast instead of broadcast (broadcast is used by default if no multicast parameters are given.) To configure multicast add one line under the <cman> section and another under the <clusternode> section:

<cman> <multicast addr="224.0.0.1"/> </cman>

<clusternode name="nd1"> <multicast addr="224.0.0.1" interface="eth0"/> </clusternode>

The multicast addresses must match and the address must be usable on the interface name given for the node.

SEE ALSO cluster.conf(5), ccs(7), cman_tool(8)