Communication benchmarks with the Ancor Fibre Channel Fabric

Conclusion

The best performances, as expected, are obtained when using the Direct Channel interface of the driver. Hereafter are summarized the best results measured, according to the hardware configuration used:

• - communications between RS/6000 250 and RS/6000 590 workstations: the overhead of the system is around 615 microseconds, and the speed can reach 12.2 MBytes/s for transmitting 65500 byte messages (Read and Write functions are implemented in a non blocking mode).

• - communications between RS/6000 C10 and RS/6000 590: the overhead of the system is around 575 microseconds, and the speed can reach 15.6 MBytes/s for transmitting 65500 byte messages (Read and Write functions are implemented in a non blocking mode).

• - communications between RS/6000 250, RS/6000 C10 and RS/6000 590 workstations: when the most powerful workstation acts as a receiver (respectively sender), on the receiver side (respectively sender side), the overhead is around 680 microseconds (respectively 630 microseconds) and the speed can reach 21.8 MBytes/s (respectively 21 MBytes/s) for 65500 byte messages (Read and Write functions are implemented in a non blocking mode).

All the results presented in this note represent maximum reachable values when implementing a parallel application in which some processing tasks will interleave the communication processes.

For the project in which we are involved (implementation of second level trigger), the size of messages to be transferred has been defined to be either 64 bytes or 1024 bytes. In this case, the corresponding performance of the system is located in left parts of graphs, where the lowest results are reported. Assuming the workstations could be RS/6000 C10 and 590 models for instance, the best communication time between two of these machines, for a 64 byte message will be around 580 microseconds and 600 microseconds for a 1024 byte message.

The next step in studying the behaviour of the Fiber Channel Fabric will be to connect several other workstations around it, and to estimate several important parameters like for instance the interference induced by the switch when several independent communications are performed in parallel, the way contention problems are managed, ...

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