btw... on the statistics page, what does "load" mean as CPU, memory and network statistics all seem the same as normal but "load" has pretty much doubled.
Eth2 is connected directly to a host server with a cross-over cable, as it happens this server is out of use at the moment and shut down, to further rule out problems with this connection I've disconnected the cable but performance is still bad.
Each host server is connected to the SAN with a separate x-over connection which put me off the idea of a network problem.
Performance is good again now, the SAN has been back in production for 3 days and is running great. It seems that the RAID parity was corrupt, the consistency check has rectified this. I've scheduled one to run every weekend to avoid this happening again.
I still don't feel 100% secure that the SAN is ok so I'm going to keep a close eye on it I'll post back if I get any new info.