1. Stephen Gowdy FNAL 9th Feb 2015CMS Computing Model Simulation 1

2.  Want to look at different computing models  To use caching  Where to place caches  How large they need to be  Discussion with others to possibly collaborate  Writing a basic Python simulation  Can consider to change to C++ if better performance is needed 9th Feb 2015CMS Computing Model Simulation 2

3.  Event driven discrete simulation  Each job is the event  Takes account of slots in sites  Allows for perfect transfers between sites  Can check limit for internal bandwidth of site  Information on this not available in SiteDB  Code is in https://github.com/gowdy/sitesimhttps://github.com/gowdy/sitesim 9th Feb 2015CMS Computing Model Simulation 3

4.  Flat files read to load in site, network, job and file information  Setup sites and links  Next setup catalogue of data  Read in simulation parameters for CPU efficiency and remote read penalty  Start processing jobs in sequence  Use list of jobs from dashboard to feed simulation  See how it performs to process current jobs 9th Feb 2015CMS Computing Model Simulation 4

5. 9th Feb 2015CMS Computing Model Simulation 5 site cpuTime inputData fractionRead start end runTime dataReadTime dataReadCPUHit theStore Job name disk bandwidth network [[site, bandwidth, quality, latency] … ] batch Site qjobs [ Job ] rjobs [ Job ] djobs [ Job ] cores bandwidth Batch catalogue {lfn:[site…]} files [(lfn, size) …] EventStore

6.  Extracted from SiteDB pledge database  Use information for 2014, most recent update  If site has no pledge just assume 10TB and 100 slots  Tier-2s default is larger, should probably update  No internal bandwidth information so assume 20GB/s at all sites  Recently started only considering US Tier-1 and Tier-2 sites  Sizes taken by hand from REBUS (could probably automate also)  Vanderbilt assumed to be the same as others 9th Feb 2015CMS Computing Model Simulation 6

7.  Site, Start Time, Wall Clock, CPU time, files read, percentage of file read  Latter isn’t available from dashboard  Possible to get from xrootd monitoring, but how to link information?  Just use the xrootd information statistically?  Extracted job information from dashboard  From 8pm 22 nd September till midnight  About 4% of jobs have no site information (discarded)  About 1% no CPU time (use wall clock)  About 2% have no start time (use CPU time before end time)  Will compare wall clock in simulation with actual for quality of simulation check  Compare overall simulated wall clock time to compare different scenarios 9th Feb 2015CMS Computing Model Simulation 7

8.  Extract network mesh from PhEDEx  Using the links interface  Also get reliability information  If not present assumed 99%  No actual transfer rate information available for links  Use what is available to get a number between 1GB/s and 10GB/s, not at all accurate. Default 1GB/s.  Extract file location information from PhEDEx  No historical information is available  When updating job information need to get an update for file locations  Only get information on file used by jobs  740 of the 8939 looked like they read data remotely (but some will be due to stale PhEDEx info) 9th Feb 2015CMS Computing Model Simulation 8

9. 9th Feb 2015CMS Computing Model Simulation 9 Startup output when only using US T1 and T2 sites; $ python python/Simulation.py Read in 9 sites. Read in 72 network links. Read in 9982 files. Read in 6728 locations. Read in 3 latency bins. Read in 10 job efficiency slots. About to read and simulate 2611 jobs... …

10.  Need to add caching strategy later  Including cache cleaning if getting full  Cache hierarchy  Currently simulation allows no transfers, or transfers. Also can discard transfers.  Won’t transfer if there is no space available at a site  Implement different models  With new version of xrootd can read while still transferring  Actual current model of reading remotely if not present should be added 9th Feb 2015CMS Computing Model Simulation 10

11.  Run standard set of 2293 US jobs  With transferring all data for a job in serial total wall clock time is ~86.4Ms  249 jobs need to transfer at least one file, taking total of 1263s  Enabling remote read increases total time to ~87.5Ms  This is only effected by jobs that don’t have data locally  Need to update to reflect actual transfer times  Currently idealised using whole bandwidth for every transfer  Enabling parallel transfers (i.e. only considering longest one per job) reduces time  248 jobs need to transfer a file, taking total of 641s  Fairly large variations due to random numbers, converted to use seeds 9th Feb 2015CMS Computing Model Simulation 11

12.  Put all disk at the T1  Increases total job time to 99.3Ms.  Add realistic transfer times  Reallocate some disk space to CPU  Increase the load on the system till it is full 9th Feb 2015CMS Computing Model Simulation 12