Evaluation of Objectivity/AMS on the Wide Area Network

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) 175176 objects / page
• objects for the write/read
• 1,000,000 objects for LAN 570 pages
• 100,000 objects for WAN 57 pages

5
CPU Utilization for Write/Readfor V5.1 and V5.2
on LAN
AVE12
AVE18
AVE4
AVE8
6
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
Data Transfer for Write on LAN and WAN
Control Transfer Phase (CTP)
Data Transfer Phase (DTP)
Bulk Transfer
8
Data Transfer for Readon LAN and WAN
Control Data Transfer Phase (CDTP)
9
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
Bulk Data Transfer Rate for Various Window Size
(KEK - CERN)
12
Effective Bandwidthfor RTT 280 ms (KEK - CERN)
ftp
AMS
Efficiency ()
2Mbps
20Mbps
Needs the window scale option
200Mbps
Window Size
(bytes)
13
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