Thursday Jan 21, 2010

Configuration of 3rd mediator host in campus cluster

One of the new features in Sun Cluster 3.2 11/09 update3 is the Solaris Volume Manager Three-Mediator support. This is very helpful for two-room campus cluster configurations. It's recommended to install the 3rd mediator host in a third-room. Please refer to the details about the Guidelines for Mediators.
In the Solaris Cluster 3.3 docs you can find Configuring Dual-String Mediator documentation.

Advantages:
-- 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).
Consider:
-- 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
  • A) Add root to sysadmin in /etc/group
    # vi /etc/group
    sysadmin::14:root

  • B) Create metadb and dummy diskset
    # 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
  • A) Add 3rd mediator host to /etc/hosts
    # echo <ipaddress hostname> >> /etc/hosts

  • B) Add 3rd mediator host to existing diskset on one cluster node.
    # 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.

    Example output:


    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:

    Download the mediatorcheck.ksh script here!

    About

    I'm still mostly blogging around Solaris Cluster and support. Independently if for Sun Microsystems or Oracle. :-)

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