apefray

Did as you mentioned and the drives were recognised on the SATA ports. I made a mistake in my original post, where I said the UD drives were connected to the Intel expander via the Startech enclosure, but they weren't. They were connected to the SCU ports on the motherboard. So basically anything connected directly to the MB ports were working fine, and anything connected via the Intel Expander card weren't working. It turns out it was the Intel expander card that had failed for some reason.

To cut a long story short, I just went ahead and bought a 2nd hand super micro server which has a built in expander on the backplane, so I'm now using just the HP HBA to connect all the drives including the UD ones, and the Startech is now connected to the SATA ports on the MB. I then moved the parity and 2 cache drives to the Startech enclosure and it's now back up and running.

Also swapped the unraid usb boot to a new one as it had been running for 9 years, although there was nothing wrong with the old USB, just took the opportunity to update it whilst preparing the new server.

I did come across a couple of networking niggles, so had to change the server IP address, but they appear to be sorting themselves out (cache maybe).