By Juergens-Oracle on Jan 21, 2010
In the Solaris Cluster 3.3 docs you can find Configuring Dual-String Mediator documentation.
-- The 3rd mediator host is used to get the majority of Solaris Volume Manager configuration when one room is lost due to an error.
-- The 3rd mediator host only need public network connection. (Must not be part of the cluster and need no connection to the shared storage).
-- One more room necessary
-- One more host for administration, but if using a Sun Cluster quorum server then the 3rd mediator can be on the same host.
This example shows how to add a 3rd mediator host to an existing Solaris Volume Manager diskset
Configuration steps on the 3rd mediator host
# vi /etc/group
# metadb -afc 3 c0t0d0s7 c1t0d0s7
# metaset -s <dummyds> -a -h <3rd_mediator_host>
Note: Maybe a good name for the dummyds can be a combination of the used setname on the campuscluster name e.g.:'setnameofcampuscluster_campusclustername'. If using more than one set it could be e.g: 'sets_of_campusclustername'. Or if using it for more than one cluster it's possible to create one set with a specific name for each cluster. This could be helpful for monitoring/configuration purposes. But keep in mind this is not required, one set is enough for all clusters which use this 3rd mediator host.
Configuraiton steps on cluster nodes
# echo <ipaddress hostname> >> /etc/hosts
# metaset -s <setname> -a -m <3rd_mediator_host>
ATTENTION: If using 3rd mediator host for more than one cluster. Each cluster node and diskset must have a unique name throughout all clusters, and a diskset cannot be named shared or admin.
Hint1: On the cluster nodes and on the third mediator the configuration is stored in the file /etc/lvm/meddb
Hint2: Use a script to monitor the mediator status on the cluster nodes. Similar to: