Limulus Software

The following is a list of basic cluster RPMS that will be included in the software stack. The base distribution will be Scientific Linux.

Automatic Power Control

One key design component of the new Limulus Case is software controlled power to the nodes. This feature will allow nodes to be powered-on only when needed. As an experiment, a simple script was written that monitors the Grid Engine queue. If there are jobs waiting in the queue, nodes are powered-on. Once the work is done (i.e. nothing more in the queue) the nodes are powered off).

As an example, an 8 core job was run on the Norbert cluster (in the Limulus case). The head node has 4 cores and each worker node has 2 cores for a total of 10 cores. An 8 node job was submitted via Grid Engine with only the head node powered-on. The script noticed the job waiting in the queue and turned on a single worker node to give 6 cores total, which were still not enough. Another node was powered-on and the total cores reached 8 and the job started to run. After completion, the script noticed that there was nothing in the queue and shutdown the nodes.

To see how the number of nodes changes with the work in the queue, consider the Ganglia trace below. Note that the number of nodes in the cluster load graph (green line) changes from 1 to 2 then 3 then back down to 1. Similarly the number of CPUs (red line) raises to 8 then back to down to 4 (the original 4 cores in the head node). Similar changes can be seen in the system memory.