Run some tests to give a current snapshot of the % overhead that darshan introduces on BG/P, Cray, and Linux clusters. We have access to at least one example of all three. The test plan:

• use IOR with a relatively small access size (256K)
• test both shared and unique files
• do 5 samples per data point (to combat noise across runs)
• aim for 60 second runs
• weak scaling
• compare with and without darshan, both in terms of run time and ior reported performance