Hi James,
I'm no expert in these things but I wonder if it might not be caused by an electrical/USB problem rather than a filesystem one. So either a controller inside the disk, or in the caddy/enclosure, a cable, or the usb system in your server, or any intervening usb hub.
Could be. The cause doesn't necessarily matter to me, I know these things happen, what matters is whether my server stays up when a non-essential filesystem has some errors.
Did your system crash when you physically plugged in the usb disk, or when you mounted the disk?
During access. I think I was deleting some files at the time then it just froze.
I'm not sure how you'd rule this in or out, other than trying to reproduce the fault with a lot of plugging/unplugging, something you might not want to do if that server is of some importance. Maybe you could also try the same disk in a different caddy.
I wiped the disk (reformatted as xfs) and it appears to be fine so far. I was checking the disks to go into backup rotation (had been used previously at another site that had outgrown them). This disk will be used early next week so if there are any actual problems with the media I should find out then. Thanks James