vice versa. We sent these files to /dev/null to eliminate any hard disk influence on the receiver side.
The hardware requisites for this test are the same as described in Section 5.1.4.1, “SP Switch - FDDI Connection without Bridging” on page 174. The slow internal SCSI disks in two of our four nodes in SP2 would not allow the transfer rate to exceed 4.5 MB/s. Both remaining nodes in SP2 contain faster SSA hard disks that allow a transfer rate of 7.5 MB/s. Nevertheless, the overall achievable data transfer rate will not exceed the bandwidth of the FDDI connection. So we decided to start several ftp programs on nodes in SP2 and SP21 to sum up the transfer rates.
With this scenario, we again measured a cumulative transfer rate of up to 44 MB/s (observed with the freeware tool monitor) that is close to the maximum theoretical transfer rate of 4x12.5 MB/s=50 MB/s. Every node’s FDDI interface contributed an overall transfer rate of about 11 MB/s (sending and receiving). The limiting factor once again was the CPU on the four nodes in SP2 that was not able to handle more data simultaneously (100% busy, as seen with monitor). We could not find any significant influence of bridging on the measured data transfer rate.
5.1.5 SP Switch - FDDI Connection in an ADSM Environment
To get a view into a "real world" scenario and to check corresponding performance data, we established a simple ADSM environment. Four nodes in SP2 with FDDI interfaces stand for four FDDI backbones in a possible customer environment. These backbones send ADSM data via SP Switch Router to an ADSM server (see Figure 58). ADSM version 3.1.20 was installed.
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Figure 58. SP Switch Router in an ADSM Environment
Single RS/6000 SP and Single SP Switch Router 185
