The Computing Element (CE) is a portal machine for grid jobs to the local batch server. The batch system server might be located on the Compute Element or can be installed on a separate machine. In our case we setup the batch system server and the Compute Element on different machines. The grid jobs sent via Workload Management System or via direct job submission are delivered from the Compute Element to the batch system and started on a free worker node. After the job has finished the output files are copied from the worker node to the Compute Element and from the Compute Element back to the Workload Management System. All jobs are accounted and published to the MonBox (in gLite 3.1) or the gLite ApelNode (in gLite 3.2). And just like any other middleware service an ldap server provides the information of the computing resources.
On the CREAM CE several daemons ensue the right functionality. Running the service requires to open a few ports in the firewall to enable the communication to external services such as the Workload Management System and the site BDII.
On port 2170 ldap listens. The port has to be reachable by the site BDII to gather all information about the Compute Element. The web service for CREAM is listening on port 8443 via tomcat. Finally for the data transfer via gridftp port 2811 has to be open.
2170 ldap reachable by the site BDII 8443 tomcat open 2811 gridftp open
Go on with CREAM CE Installation
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