The RB is dead long live the WMS
Fri 7 Nov 2008
Four years in the development but the UK Grid is well on the way to the move from Resource Brokers (RBs) to Workload Management Servers (WMSs). Last week the RB at Imperial College London was turned off and replaced with a WMS. This was the second of the RBs supported by GridPP to be decommissioned and the final two at the Rutherford Appleton Laboratory are planned to be taken out of service at the end of the month.
The gLite WMS is a welcome improvement to the RBs which suffered numerous service stability and job throughput limitations. In the UK three sites ran RB services - Glasgow, Imperial and RAL. Jeremy Coles of GridPP is really happy with how it is going "Over the last 6 months we have had WMS services deployed at these sites and slowly (as we built up confidence) replaced the RBs in production".
The WMS is a set of services and clients that broker job submissions to Computing Elements at the Grid sites. One of the most important criteria for use of the WMS was that it must be able cope with at least 10,000 jobs per day for more than 5 consecutive days without failing, and at the end of this period less than 1% of jobs should be "stale" (for example jobs that fail to progress beyond the submitted stage). One of the major improvement of the WMS over the RB is that bulk submission is possible whereby sets of independent jobs with similar requirements and priority can be matched to resources in a single operation. Service stability has also been improved through the introduction of load limitation which stops job submission when the load on the WMS gets too high.
From a users perspective, however, the move is not transparent and submitting to a WMS requires use of a different command set.
For the basics of job submission see the EGEE wiki http://wiki.egee-see.org/index.php/SG_Running_Jobs_WMProxy_CLI.
There are also numerous new JDL options which can be found in the guide here: https://edms.cern.ch/file/590869/1/EGEE-JRA1-TEC-590869-JDL-Attributes-v%200-9.pdf.
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