Overview of DiaGrid
DiaGrid uses Condor, developed at the University of Wisconsin, to issue, manage, and migrate computational work among available computer systems.
Condor is a specialized workload management system for compute-intensive jobs. Like other full-featured batch systems, Condor provides a job queueing mechanism, scheduling policy, priority scheme, resource monitoring, and resource management. Users submit their serial or parallel jobs to Condor. Condor then places these jobs into a queue and chooses when and where to run the jobs based upon a policy. Condor carefully monitors their progress and ultimately informs the user upon their job's completion.
While providing functionality similar to that of a more traditional batch queueing system, Condor's novel architecture allows it to succeed in areas where traditional scheduling systems fail. Condor can be used to manage a cluster of dedicated compute nodes (such as a "Beowulf" cluster). In addition, unique mechanisms enable Condor to effectively harness wasted CPU power from otherwise idle desktop workstations. For example, Condor can be configured to only use desktop machines where the keyboard and mouse are idle. Should Condor detect that a machine is no longer available (a key press is detected), in many circumstances Condor is able to transparently produce a checkpoint and migrate a job to a different machine which is currently idle. Condor does not require a shared file system across machines. If no shared file system is available, Condor can transfer the job's data files on behalf of the user, or Condor may be able to transparently redirect all the job's I/O requests back to the submit machine. As a result, Condor can be used to seamlessly combine all of an organization's computational power into one resource.
