End-to-End performance tuning Brian Davies Gridpp28 Manchester 2012

18/04/2012 End-End performance tuning 2 Areas of Improvements FTS –# Streams –# Files –Tx Timeout –Preparing File Ratio –Copy Mechanism G-U-C vs srmcp Asynchronous Ptp Access Method –Synchronous vs Asynchronous calls –Scheduled vs unscheduled connections. –Srm-less –Federated xrootd Costs as well as benefits TCP/ Window Tuning Jumbo Frames –Some changes only see benefit in end site also make changes. WN-WAN tuning –Tcp Window size –‘Nat’ing –Xrootd configuration/optimisation.

18/04/2012 End-End performance tuning 3 Other areas of optimisation?? Homogenous network –Mixing WN and Disk Servers can easily reduce network bandwidth VM components –Splitting services Databases –Type –Separate node –Internal operation Cleansing –EG DPM requests DB DNS Aliasing of multiple machines Knowledge transfer

18/04/2012 End-End performance tuning 4 Who does optimisation and when is the benefit seen. Some optimisations can be unilateral. FTS tuning, database improvements etc. –Others have to be co-ordinated Jumbo Frames Some optimisation benefits seen straight away. –Others require end host to make changes before benefit is seen. An “improvement” at one site may degrade another site. –TCP tuning at QMUL/RHUL

18/04/2012 End-End performance tuning 5 Differences between T1 and T2s? (Some) Current T1 issues will/are problems that a “large” T2 will face in X* years time. Problems a T2 are facing now may have been solved by (a) T1 Y* years ago. A site should/does not need try to re-solve a problem(s) that another site(s)/tier has solved in the past. *(Where X and Y are to be determined).

18/04/2012 End-End performance tuning 6 Manchester Network improvements Transfers from Manc’ to T1s

18/04/2012 End-End performance tuning 7 Manchester network improvements Reverse direction

18/04/2012 End-End performance tuning 8 Manchester Network improvements Transfers from Manc’ to UK T2s

18/04/2012 End-End performance tuning 9 Manchester Network improvements Transfers from Manc’ to Non UK T2s

18/04/2012 End-End performance tuning 10 Manchester Network improvements

18/04/2012 End-End performance tuning 11 Effect of streams on RALPPD-T1s Failing transfers required number of threads per transfer to have to be reduced to 1 per file transfer.` –Deemed more important to receive data from CERN than getting good rate for other sites Mitigated overall throughput by increasing number of concurrent transfers. –Individual file transfer speed reduced and latency increased. Once underlining issue re-solved returned to previous settings.

18/04/2012 End-End performance tuning 12 Effect of streams on T1s- RALPPD #Streams reduced/Increased Effects transfers TO the site. Effects Some T1s more than others

18/04/2012 End-End performance tuning 13 Effect of streams on RALPPD- T1s No (known) changes in streams in reverse direction

18/04/2012 End-End performance tuning 14 Other areas of optimisation?? “In the wiki” –But where? Which wiki? ????