I had 16 of them 15 years ago, they all stopped working over the years... I even had the data sled they all mounted into, from an editbox!

looks so good from the outside!

What a beast. I bet it weighs a ton. LOL. I really hope the SD versions work. It would make life so much easier for you.

So Quantel made their own bespoke RAID0 drive array, likely it is semi sort of SCSI on the interconnect, and yes you do probably need all the disks to be the same type for it to work, as they probably assign each of them a sector of data in a big buffer RAM, and have all the internal buses reading and writing that data out. At least with the adaptor cards they will likely work, just have to have them be exactly the same size as the original, and so long as they are as fast or faster so the other drives are the limit, they will work no issue. bonus if you go for all SSD you can get the biggest size SD cards, and emulate the largest SCSI devices ever, and hopefully still have the Quantel think this disk is the biggest SAN it has ever seen.

If they use any uncommon SCSI feature, I'm pretty sure your ZuluSCSI (or any other SCSI emulator) will not work properly. For example it could check the SCSI mode pages (basically a configuration system) for specific settings or ID strings (model number etc.), I am not sure the ZuluSCSU can replicate that. Also, some more obscure SCSI commands are not at all implemented in the open-source emulators. Performance might not be entirely up to spec, depending on the SD card interface, leading to "tail latency" where one disk is slower than all others, decreasing performance (and possibly worse in a soft-realtime application like this). If they use the custom (undocumented) pin headers on the harddisks at all, you're probably entirely out of luck (those could be signals like out-of-band data, diagnostic serial port, spindle sync, etc.)

if it's still partly scsi over that big cable, chances are you can replace the whole thing with one ssd and a translator board

Sorry to hear 'bout the power supply. Isn't it always the way, you go to test the component and it catastrophically fails 🤔. Dylan will ride again, I am sure of it.

Stupid question, have you asked Fujitsu if they have spare drives?. I know when I worked there our warehouse had amazing variety of obscure bits. Probably worth contacting the Manchester office

expensive hobby those fujitsis go for 3-400 usd