This section contains the following information and procedures:
A dual-string mediator, or mediator host, is a cluster node that stores mediator data. Mediator data provides information on the location of other mediators and contains a commit count that is identical to the commit count stored in the database replicas. This commit count is used to confirm that the mediator data is in sync with the data in the database replicas.
Dual-string mediators are required for all Solstice DiskSuite or Solaris Volume Manager disk sets that are configured with exactly two disk strings and two cluster nodes. A disk string consists of a disk enclosure, its physical drives, cables from the enclosure to the node(s), and the interface adapter cards. The use of mediators enables the Sun Cluster software to ensure that the most current data is presented in the instance of a single-string failure in a dual-string configuration. The following rules apply to dual-string configurations that use mediators.
Disk sets must be configured with exactly two mediator hosts. Those two mediator hosts must be the same two cluster nodes that are used for the disk set.
A disk set cannot have more than two mediator hosts.
Mediators cannot be configured for disk sets that do not meet the two-string and two-host criteria.
These rules do not require that the entire cluster must have exactly two nodes. Rather, only those disk sets that have two disk strings must be connected to exactly two nodes. An N+1 cluster and many other topologies are permitted under these rules.
Perform this procedure if your configuration requires dual-string mediators.
Become superuser on the node that currently masters the disk set to which you intend to add mediator hosts.
Run the metaset(1M) command to add each node with connectivity to the disk set as a mediator host for that disk set.
# metaset -s setname -a -m mediator-host-list |
Specifies the disk set name
Adds to the disk set
Specifies the name of the node to add as a mediator host for the disk set
See the mediator(7D) man page for details about mediator-specific options to the metaset command.
Check the status of mediator data.
The following example adds the nodes phys-schost-1 and phys-schost-2 as mediator hosts for the disk set dg-schost-1. Both commands are run from the node phys-schost-1.
# metaset -s dg-schost-1 -a -m phys-schost-1 # metaset -s dg-schost-1 -a -m phys-schost-2 |
Add mediator hosts as described in How to Add Mediator Hosts.
Run the medstat command.
# medstat -s setname |
Specifies the disk set name
See the medstat(1M) man page for more information.
If Bad is the value in the Status field of the medstat output, repair the affected mediator host.
Go to How to Fix Bad Mediator Data.
Go to How to Create Cluster File Systems to create a cluster file system.
Perform this procedure to repair bad mediator data.
Identify all mediator hosts with bad mediator data as described in the procedure How to Check the Status of Mediator Data.
Become superuser on the node that owns the affected disk set.
Remove all mediator hosts with bad mediator data from all affected disk sets.
# metaset -s setname -d -m mediator-host-list |
Specifies the disk set name
Deletes from the disk set
Specifies the name of the node to remove as a mediator host for the disk set
Restore each mediator host that you removed in Step 3.
# metaset -s setname -a -m mediator-host-list |
Adds to the disk set
Specifies the name of the node to add as a mediator host for the disk set
See the mediator(7D) man page for details about mediator-specific options to the metaset command.
Create cluster file systems.