Clusters

A cluster is a group of machines or other resources that act as one powerful system. Clustering provides high availability, continuous operations for a long time. There are many varieties of clusters.

This scenario uses openMosix, a Linux kernel extension for clustering. The openMosix cluster is a single-image cluster: multiple copies of a single operating system kernel.

openMosix joins Linux machines to function as one large multiple-processor computer. If you have a 12-node cluster, it is as though you had one computer with the CPU power of 12 computers. One process will not be 12-times faster, but you can run 12 processes simultaneously.

The openMosix package is not available from any one distribution. You can download it from the project site.

Notice that after the profile is set up, cluster creation is automated. You could create an opposite profile that would undo the actions of this scenario, thereby unclustering the machines. You could set both profiles to run on a schedule, which would cluster and uncluster your resources according to your needs.

Creating an openMosix Cluster with Sun Update Connection – Enterprise

This procedure to create a cluster with nodes takes about two hours to complete. It might take less time if there are no unexpected problems or a little more time for different environments. Maintenance tasks on the cluster (for example, adding or changing a node) take about five to ten minutes.

To Create an openMosix Cluster with Sun Update Connection – Enterprise

1. Choose the machines that will be nodes of the cluster.

   Each machine should have a Linux distribution that is supported by Sun Update Connection – Enterprise and the kernel version supported by openMosix.

2. Install Sun Update Connection – Enterprise (system dependency server [SDS], dependency manager [DM], the knowledge base, the console, and the agent) on one of the machines.

   See the Sun Update Connection - Enterprise 1.0 Administration Guide.

3. Install the agent on the other machines.

4. Add the openMosix RPM to the local knowledge base.

   The Local Expansion technology creates deployment rules.

   See Adding Undetected Linux Software.

5. In a text editor, create /etc/mosix.map.

   This file maps a node number to each IP address.

6. Add a file declaration called /etc/mosix.map

   See Creating File Declarations.

7. Add the /etc/mosix.map file to the local knowledge base.

   See Uploading Local Configuration Files.

8. In a text editor, create a version of /etc/hosts which includes the hosts to be in the cluster.

9. Add a /etc/hosts file declaration and add the version you just made to the local knowledge base.

   See Creating File Declarations and Uploading Local Configuration Files.

10. Write a script that changes the default boot kernel to openMosix in the grub table:

    OpenMosixAsDefault.sh

    See Writing Actions.

11. Add this script to Local/Pre-actions.

    See Uploading Actions.

12. Add this script to Local/Post-actions.

    See Uploading Actions.

13. Create a profile called openMosixNode that defines the following requirements of a node in the cluster:

    • Required: openMosix kernel and management tools

    • Required: /etc/mosix.map (specifying local version)

    • Required: /etc/hosts (specifying local version)

    • Required: Pre-action OpenMosixAsDefault.sh

    See To Create a Profile.

14. Create a group called Test, which includes two of the machines, and then Create a group called openMosixCluster, which includes all the machines that are to be nodes in the cluster.

    See To Create a Group.

15. Create a job that runs in simulate mode on the Test group, with the following profile tasks:

    • openMosixNode profile

    • Perform Restart

      Check the estimates and status of the job before continuing. See Creating Complex Jobs.

16. Rerun the job in deploy mode on the Test group. Check the results and status of the hosts before continuing.

    See To Rerun a Job.

17. Run the job again in deploy mode on the openMosixCluster group.

    All selected machines are now nodes of a cluster. See Creating Complex Jobs.

To Add a Node to the Cluster

1. Install the agent on the new machine.

   See the Sun Update Connection - Enterprise 1.0 Administration Guide.

2. Add this managed host to the openMosixCluster group.

   See To Edit a Group.

3. Open the mosix.map knowledge base file and add a new node number and the IP of the new machine.

   Open the /etc/hosts knowledge base files and add the new host name.

   See Opening Host Files.

4. Run the job with the openMosixNode profile in deploy mode on the openMosixCluster group.

   Legacy data and applications are not touched by the job, but the new map and hosts files are downloaded to each node. See Creating Complex Jobs.