heterogenous clusters

[Alan Ward]

I'm wondering if other people on this list have experimented
with heterogenous clusters or Beowulfs: i.e. different hardware
and operating systems? Two points interest me particularly:

1) What communication systems and programming languages?
(I use direct socket communications and Java).

2) When you slice up a job to distribute it between nodes,
how does slice size affect performance when large speed
differences exist (i.e. ratios of 1:2 up to 1:5)?
My experience indicates that (a) too small a slice gives you a
large communication overhead, and (b) too large a slice makes
you lose time at overall completion while the slower nodes 
finish up their last slice.

Comments anybody?

Best regards,
Alan Ward