Date Added: Feb 2013
This paper describes the use of a distributed cloud computing system for High-Throughput Computing (HTC) scientific applications. The distributed cloud computing system is composed of a number of separate Infrastructure-as-a-Service (IaaS) clouds that are utilized in a unified infrastructure. The distributed cloud has been in production-quality operation for two years with approximately 500,000 completed jobs where a typical workload has 500 simultaneous embarrassingly parallel jobs that run for approximately 12 hours. The authors review the design and implementation of the system which is based on pre-existing components and a number of custom components.