[PaulClayton]

Got very fustrated, and went one better. I trashed my vios and client partition, and re-initialised the P6 managed system, and rebuilt the vios and client partition.
Now I am getting 220MBytes/second throughtput, through a 4 disk stripe with a 1Mb stripe width.
I wonder if the fact that the server was initially factory configured, whether this had not played a part in the problem, and the re-initialization resolved the problem.
The results are dramatic, and now a number of other items are now working that did not work well, including network and fabric failover.
Thanx for you inputs.