The Compute Element (CE)

In the context of the LCG grid, a computing element is defined as a grid batch queue and takes the form [hostname]:[port]/[batch-queue-name]. Accordingly, several queues for the same hostname denote different computing elements. A computing element is composed of a node acting as a grid gate (GG) to a farm of worker nodes (WN). In traditional HPC terminology, this is effectively a management / login node (grid gate) attached to a cluster of compute nodes.

The GG node is responsible for providing various services including the Globus gatekeeper, the Globus GRAM (Globus Resource Allocation Manager), the master server of a Local Resource Management System (LRMS - in this deployment the LRMS is PBS) together with the local Logging and Bookkeeping server. Whilst the WN's require only outbound connectivity (i.e. they can be on a private network address range), the GG needs to be accessible from outside the site so that it can accept jobs and dispatch them to the WN's.