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 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

Testbed Configuration Monitored CPU/Packet/…

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

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

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

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

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

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

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

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

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

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

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