Job Management Services. Three major components constituting the Job Management Services group are Computing Element, Workload Management and Accounting. Although primarily related to the job management services; accounting is a special case as it will eventually take into account not only computing, but also storage and network resources. • Computing Element (CE) is the service representing a computing resource. It provides a virtualization of the computing resource localized at a site (typically a batch queue of a cluster but also supercomputers or even single workstations). It provides information about the underlying resource and offers a common interface to submit and manage jobs on the resource. CE includes: a Grid Gate (GG) - Gatekeeper for CE based on Globus - which acts as a generic interface to the cluster; LRMS (sometimes called batch system); the cluster itself - a collection of Worker Nodes (WN) or just one multiprocessor WN, the node(s) where the jobs are run. There are two GG implementations in gLite 3.0: the LCG-CE and the gLite-CE; sites can choose what to install. The GG is responsible for accepting jobs and dispatching them for execution on the WN(s) via the LRMS. Another type of CE developed in EGEE project is CREAM (Computing Resource Execution And Management). It is a simple, lightweight service that implements all the operations required at the CE level. Its interface is defined using WSDL. The service is compliant with the existing BES standard. CREAM can be used by the WMS, via the ICE component (see next description of WMS), or by a generic client, e.g. an end-user willing to directly submit jobs to a CREAM CE. A C++ command line interface and Java clients are available for this purpose. The interface of gLite-CE and CREAM with the underlying LRMS is implemented via BLAH. All the resource management systems supported by BLAH are automatically supported by the CEs. In gLite 3.0 the supported LRMS types are OpenPBS, LSF, Maui/Torque, BQS and Condor. • Workload Management System (WMS) is a Grid level meta-scheduler that schedules jobs on the available CEs according to user preferences and several policies. It also keeps track of the jobs it manages in a consistent way. The core component of the WMS is the Workload Manager (WM), whose purpose is to accept and satisfy requests for job management coming from its clients (i.e., computational job submission). In particular the meaning of the submission request is to pass the responsibility of the job to the WM. T...
