“When looking to buy a used car, you kick the tires, make sure the radio works, check underneath for leaks, etc. You should be just as careful when deciding which nodes to use to run job scripts. At the NASA Advanced Supercomputing Facility (NAS), our prologue and epilogue have grown almost into an extension of the O/S to make sure resources that are nominally capable of running jobs are, in fact, able to run the jobs. This presentation describes the issues and solutions used by the NAS for this purpose.”