Chapter 11. Scheduling Software

Basically, scheduling software lets you run your cluster like a batch system, allowing you to allocate cluster resources, such as CPU time and memory, on a job-by-job basis. Jobs are queued and run as resources become available, subject to the priorities you establish. Your users will be able to add and remove jobs from the job queue as well as track the progress of their jobs. As the administrator, you will be able to establish priorities and manage the queue.

Scheduling software is not a high priority for everyone. If the cluster is under the control of a single user, then scheduling software probably isn't needed. Similarly, if you have a small cluster with very few users or if your cluster is very lightly used, you may not need scheduling software. As long as you have more resources than you need, manual scheduling may be a viable alternative-at least initially. If you have a small cluster and only occasionally wish you had scheduling software, it may be easier to add a few more computers or build a second cluster than deal with the problems that scheduling software introduces.

But if you have a large cluster with a growing user base, at some point you'll want to install scheduling software. At a minimum, scheduling software helps you effectively use your hardware and provides a more equitable sharing of resources. Scheduling software has other uses as well, including accounting and monitoring. The information provided by good scheduling software can be a huge help when planning for the future of your cluster.

There are several freely available scheduling systems from which you can select, including Portable Batch System (PBS), Maui, Torque, and Condor. OSCAR includes Portable Batch System (PBS) along with Maui. Torque is also available for OSCAR via opd. Rocks provides a PBS roll that includes Maui and Torque and a second roll that includes Condor. Since PBS is available for both OSCAR and Rocks, that's what's described in this chapter. (For more information on the alternatives, visit the web sites listed in the Appendix A.)

PBS is a powerful and versatile system. While this chapter sticks to the basics, you should keep in mind that there is a lot more to PBS than described here. Look at the Administrator Guide to learn more, particularly if you need help with more advanced features.