AB379B - PCI-X Dual Channel 4Gb/s Fibre Channel Adapter Performance Paper for Integrity Servers
4
Service Demand
Service demand is the amount of CPU utilized per megabyte of data transferred. This metric is measured for
small size I/O operations because large size I/Os by their nature have very small service demand. AB379B
offers low CPU service demand for small size I/O operations. To measure service demand of the AB379B,
sequential read and write operations of 1K, 4KB and 8KB I/O sizes were performed on the 8-way rx6600
system.
The following table shows single and dual port throughput and CPU utilization for sequential reads and
sequential writes with 1KB, 4KB, and 8KB I/O sizes.
AB379B Service Demand
Sequential Read
1KB 4KB 8KB
Number
of Ports
Tput
1
CPU
2
SD
3
Tput
1
CPU
2
SD
3
Tput
1
CPU
2
SD
3
Single 106 19.7%
14.8
380 16.8%
3.5
392 9.1%
1.9
Dual 204 50.4%
19.8
747 42.8%
4.6
772 20.9%
2.2
Sequential Write
1KB 4KB 8KB
Number
of Ports
Tput
1
CPU
2
SD
3
Tput
1
CPU
2
SD
3
Tput
1
CPU
2
SD
3
Single 104 19.4%
14.9
388 17.1%
3.5
377 9.0%
1.9
Dual 203 46.4%
18.3
734 39.1%
4.3
767 20.8%
2.2
NOTE:
1
Throughput in MB/s (10^6 bytes/second)
2
CPU utilization percentage (aggregate % of CPU utilized across the 8 CPUs on the rx6600)
3
Service Demand in milliseconds of CPU per megabyte, calculated as (%CPU utilization)*(number of CPUs)*10/(MB/s Throughput)
The AB379B service demand compares favorably with the previous generation A6826A 2Gb FC adapter. The
service demand metric is highly dependent on the host system processor and memory speeds. Thus any
comparison of service demand numbers must be with respect to the same processor and system type.
To provide this comparison, the service demand tests were performed on the same rx6600 system using the
A6826A dual-port 2Gb/s FC adapter. The following table shows the corresponding A6826A service demand:
A6826A Service Demand
1KB 4KB 8KB Number
of Ports
Read Write Read Write Read Write
Single 18 21 4.2 4.7 2.4 2.8
Dual 17 18 3.5 3.7 2.0 2.0
The single port service demand is uniformly lower on the AB379B as compared to the A6826A. The dual port
service demand on the AB379B is slightly higher.