B4 Application Environment Load Balancing Job and Queue Management Tim Smith CERN/IT

2001/05/25Tim Smith: LCCWS in FNAL2 Application Environment (I) Q: How to ensure compatibility between execution and development environments  Accessing ‘static’ system and application tools  Remote: Shared file system  Local:  Tools for client synchronisation  ‘Pre-compiler’ to hide target differences  Defining environment variables  Group accounts: Useful, but bad for security / auditing  Framework for environment definition

2001/05/25Tim Smith: LCCWS in FNAL3 Application Environment (II)  Accessing user files and application libraries  Remote:  Shared file system  Put / get mechanisms  Local:  Ship libraries with the job  Tool for sinking to clients  Static vs dynamically linked binaries  Dynamic has little benefit on a 2 processor batch  Security issues with picking up random libraries on scavenger nodes that are not managed centrally  Some 3 rd party libraries only available dynamically

2001/05/25Tim Smith: LCCWS in FNAL4 Load Balancing  Interactive: DNS (vs scripts)  Round robin vs Metric based  Since can’t predict future state  Sophistication level: load, # sessions, …  Dealing with load anomalies: true interactive functions  Batch  Over-subscribing CPUs  Internal blocking VS Context switching  Queue abuse  Master Configuration  Queue length, scheduling complexity

2001/05/25Tim Smith: LCCWS in FNAL5 Job and Queue Management  Delegated responsibilities  Tuning  Host affinities  Priorities  Regulation  Difficulty of config. and interpret. of fair-shares  Job dispatching  Forecasting  Explaining pending status  Diagnosing and reacting to ‘bad hosts’  Scalability issues due to job volume  Accounting and dispatching