Oh zark, I'm an idiot.
A couple of days ago, before work got in the way, as part of the increasingly silly and uncontrollable copying-and-backing-up, I thought I'd have a go at using eSATA. It seems a bit archaic now, but it should be quite quick, and offers an external attachment that doesn't rely on the USB bus (bus) so should allow fast transfer between an external (USB-connected) drive and another external drive. I outfitted (infitted?) one of the old desktops (the Rock) with a eSATA card at some point, and have an eSATA to SATA cable (it also had a USB cable inline for power).
I took a 1TB drive (3.5”, if you want to already guess where this falls down) and plugged it in to the card and a USB port. Nothing. Tried another USB port, and still nothing.
I tried updating drivers, thinking it might not be available to the system since the last Win10 IoT install, but that didn't help. Assuming the eSATA card had died, I ditched the idea and thought next about trying the cable with one of the T410s, which have eSATA ports.
(Have you seen my error? I didn't until just now…)
A brainwave today made me realise that I'd been attempting to use a HDD that required a 12V supply, which neither the eSATA (I don't think) nor the USB port can supply. What a wally.
Let's try it again with a 2.5” drive and its 5V requirements.
1730
Still nothing. Quelle surprise. Other than the surprise at finding out that maybe I'm not an idiot.