Beowulf Batch Processors and Job Schedulers

Edward L. Haletky and Patrick Lampert

Beowulf and grid technology provide an attractive mechanism to build powerful compute clusters with inexpensive off-the-shelf components. Yet this technology also introduces new and complex scheduling problems. How do you distribute your work over the cluster? Can you schedule your work for times of lower activity? These issues are addressed by a variety of job-scheduling and load-balancing software tools that we will examine in this article. We review seven different queuing engines that can manage your resources, schedule jobs, and even interlock runs based on execution dependencies. These seven systems range from the simplest cron-related tools to grid engines.

We will examine ease of installation, configuration, creation of a single queue, the steps required to submit an extremely simple job, as well as the steps to dispatch jobs based on time of day without using cron to enable and disable queues. Furthermore, we will comment upon availability of multi-node capability, support, and security, then present a simple chart to assist you in picking your Job Scheduling/Queuing Software.

The systems discussed are: at(1)/bbq(1), Clusterware/Load Sharing Facility (LSF), Condor, Generic Network Queuing System (GNQS), GNU Queue, Open Portable Batch System (OpenPBS), and the Sun Grid Engine (SGE). Although two of these systems are primarily grid engines (Condor and SGE), they all provide a way to queue up jobs for execution as the resources allow.

Each system was installed upon a Scyld Beowulf cluster with six slave nodes comprising off-the-shelf spare parts. Installation of the queuing agents took place on the master node leaving the six slave nodes as computational nodes.