Maintaining a PowerHA SystemMirror cluster
PowerHA® SystemMirror® systems have different maintenance tasks.
- Starting and stopping cluster services
- Various methods for starting and stopping cluster services are available.
- Maintaining shared logical volume manager components
- Any changes to logical volume components must be synchronized across all nodes in the cluster. Using C-SPOC (the Cluster Single Point of Control) to configure the cluster components on one node and then synchronize the cluster saves you time and effort.
- Managing the cluster topology
- Any changes to cluster configuration must be propagated across all nodes. Managing the cluster topology describes how to modify cluster topology after the initial configuration. You can make most changes on one node and then synchronize the cluster.
- Managing cluster resources
- Any changes to cluster resources require updating the cluster across all nodes. You can make most changes on one node and then synchronize the cluster.
- Managing cluster resource groups
- The Managing resource groups in a cluster section describes how to modify cluster resource
groups after the initial configuration. You can add or delete resources and change the runtime
policies of resource groups.
You can dynamically migrate resource groups to other nodes and take them online or offline by using the Resource Group Management utility (clRGmove) from the command line or by using SMIT.
- Managing users and groups in a cluster
- PowerHA SystemMirror allows you to manage user accounts for a cluster from a Single Point of Control (C-SPOC). Use the C-SPOC SMIT panels on any node to create, change, or remove users and groups from all cluster nodes by executing a C-SPOC command on any single cluster node.
- Managing cluster security and inter-node communications
- You can protect access to your PowerHA SystemMirror cluster by setting up security for cluster communications between nodes.
- Understanding the /etc/cluster/rhosts file
- The /etc/cluster/rhosts file
A Cluster Communications daemon (clcomd) runs on each PowerHA SystemMirror node to transparently manage inter-node communications for PowerHA SystemMirror.
In other words, PowerHA SystemMirror manages connections for you automatically:
- Populate the /etc/cluster/rhosts file with the host names or IP addresses of each node that will form the cluster.
- The clcomd command validates the addresses of the incoming connections to ensure that they are received from a node in the cluster. The rules for validation are based on the presence and contents of the /etc/cluster/rhosts file.
- If the /etc/cluster/rhosts file is not present, clcomd rejects all connections
After you synchronize the cluster, you can empty the /etc/cluster/rhosts file (but not remove it), because the information present in the PowerHA SystemMirror Configuration Database would be sufficient for all future connections.
- The ~/.rhosts File
- PowerHA SystemMirror does not use native AIX® remote execution (rsh) so you do not need to configure a ~/.rhosts file unless you intend to use Workload Partitions (WPAR) which have their own requirements on this file.
- Saving and restoring PowerHA SystemMirror cluster configurations
- After you configure the topology and resources of a cluster, you can save the cluster configuration by taking a cluster snapshot. This saved configuration can later be used to restore the configuration if this is needed by applying the cluster snapshot. A cluster snapshot can also be applied to an active cluster to dynamically reconfigure the cluster.