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Evaluation of Objectivity/AMS on the Wide Area Network

Evaluation of Objectivity/AMS on the Wide Area Network. SATO Hiroyuki KEK Computing Research Center. Introduction. Measured the performances of Objectivity/AMS : AMS write/read access (5.1 vs 5.2) AMS over LAN and WAN

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Evaluation of Objectivity/AMS on the Wide Area Network

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  1. Evaluation of Objectivity/AMSon the Wide Area Network SATO Hiroyuki KEK Computing Research Center

  2. Introduction • Measured the performances of Objectivity/AMS : • AMS write/read access (5.1 vs 5.2) • AMS over LAN and WAN • Resource utilization of the AMS server is monitored for 5.1 and 5.2 on LAN • CPU utilization • TCP/IP packet was monitored for AMS transaction over LAN and WAN. • Transfer rate

  3. Testbed Configuration Monitored CPU/Packet/…

  4. AMS/Write-Read Performance Test on LAN and WAN • Objectivity page size is 8192 bytes • Test object (40 bytes) : 175~176 objects / page • #’objects for the write/read : • 1,000,000 objects for LAN : 570 pages • 100,000 objects for WAN : 57 pages

  5. 40 40 30 30 CPU Utilization (%) CPU Utilization (%) Write 20 20 10 10 0 0 0 0 20 20 40 40 60 60 Time (sec) Time (sec) 30 30 20 20 CPU Utilization (%) CPU Utilization (%) Read 10 10 0 0 0 0 20 20 40 40 60 60 80 80 100 100 Time (sec) Time (sec) V5.1 V5.2 CPU Utilization for Write/Readfor V5.1 and V5.2 on LAN AVE:12% AVE:18% AVE:4% AVE:8%

  6. Round Trip Time between KEK and CERN 500 (msec) 400 300 0 10 20 30 Day in 2000 Measurements on the WAN • Characteristics of the network between KEK and CERN • RTT (Round Trip Time) is about 300 msec • The bandwidth is 2Mbps

  7. Server (AMS) at KEK Client at KEK/CERN 1200 1200 1000 1000 52 bytes 800 800 Transfer Rate (kB/s) Transfer Rate (kB/s) 600 600 LAN 8236 bytes 400 400 8280 bytes 200 200 0 0 36 bytes Time (sec) 8280 bytes WAN 0 0 20 20 40 40 60 60 80 80 (sec) Time Data Transfer for Write on LAN and WAN Control Transfer Phase (CTP) Data Transfer Phase (DTP) Bulk Transfer

  8. Server (AMS) at KEK Client at KEK/CERN 500 500 52 bytes 400 400 Transfer Rate (kB/s) Transfer Rate (kB/s) RTT 8236 bytes LAN 300 300 200 200 100 100 0 0 0 25 50 75 100 Time (sec) x 103 4200 Write Seq. Number 4100 WAN Read 4000 0 1 2 0 50 100 150 200 Time (sec) Time since #’4M is sent (sec) Data Transfer for Readon LAN and WAN Control Data Transfer Phase (CDTP)

  9. 140 120 100 80 60 40 20 0 Comparison with AMS Writeand ftp Write performance over WAN is faster than ftp ! Transfer Rate (kB/s) AMS ftp 0 20 40 60 80 (sec) Time

  10. Window Size in TCP/IP • Monitored with tcpdump • AMS : 33580 bytes • ftp : 24820 bytes • Window size affects the transfer rate • It can be changed with “setsockopt” function (standard max : 65535 bytes / optional 232 bytes) • Bulk data transfer rate for various received window size is measured

  11. 02/Feb/2000 250 Window size 200 64240 bytes (Test Program) Data Transfer Rate (kB/s) 150 33580 bytes (Objectivity) 100 50 24820 bytes (ftp) 0 0 6 12 18 24 (hour) Time Bulk Data Transfer Rate for Various Window Size (KEK - CERN)

  12. 10 2 10 1 Window Size RTT Bandwidth 1 Efficiency = 10 -1 10 -2 10 3 10 4 10 5 10 6 10 7 Effective Bandwidthfor RTT = 280 ms (KEK - CERN) ftp AMS Efficiency (%) 2Mbps 20Mbps Needs the window scale option 200Mbps Window Size (bytes)

  13. CERN 1 KEK Read 1 2 2 3 3 4 satellite (RTT=655ms) 4 5 3 5 6 6 7 7 8 8 9 ack2 2 Transaction Time / Page (sec) 10 10 11 11 ack4 12 TCP Timeout 12 13 1 13 ack6 surface (RTT=300ms) 14 14 15 15 16 16 9 0 9 ack8 100 150 200 ack8 ack8 Page Number ack8 ack8 8236 = 536*15+196 ==> 16 segmets ack8 ack8 MSS for satellite ack16 Comparison with network of surface and satellite LOST! ack8 The congestion window is initialized after this transaction.

  14. Summary • Write/Read operation of Objectivity 5.2 works on the WAN • AMS server 5.2 is multi-threaded • Consumes more CPU cycles than 5.1 • Does not matter when network is a bottleneck • Write performance over WAN is faster than ftp • more speedup is expected with a larger window size (Optimal window size may vary with the available buffer size of the network router) • Read performance is poor due to the hand-shaking • Oscillation of congestion window is observed in satellite network — further study needed

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