end-to-end performance tuning brian davies gridpp28 manchester 2012

End-to-End performance tuning

Brian DaviesGridpp28

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.


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


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


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).


Manchester Network improvements

•Transfers from Manc’ to T1s


Manchester network improvements

•Reverse direction



•Transfers from Manc’ to UK T2s



•Transfers from Manc’ to Non UK T2s


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.


Effect of streams on T1s-RALPPD

•#Streams reduced/Increased•Effects transfers TO the site.

Effects Some T1s more than others


Effect of streams on RALPPD-T1s

No (known) changes in streams in reverse direction


Other areas of optimisation??

• “In the wiki”– But where?

• Which wiki?

• ????

end-to-end performance tuning brian davies gridpp28 manchester 2012

Documents