So… everything went exactly according to plan yesterday with my hard drive juggling: the data copy finished up on Saturday morning, the system booted from the new drives after some boot loader fiddling, and the arrays rebuilt in to full redundant mode once I added the two 500GB drives from the old array.
There was just one snag — I had to sacrifice my desktop PC.
Everything was going perfectly until I took the new 1TB drives, brimming with data, and placed them in to the TV box. It was a nice system about five years ago, but neither of the SATA controllers on the motherboard would detect those shiny new drives, despite putting jumpers in place to switch the drives in to SATA 1.5 Gbit/s compatibility mode. With no other option at hand, I swapped the TV box for my desktop box and got everything working there instead.
It’s actually quite nice having that box in the lounge, now — it’s super-quiet, and it has no trouble playing HD streams. I’ve put the old TV box back together as a desktop for now, but with just 512MB of RAM it doesn’t have the grunt to run my usual selection of music apps.
One option to solve this would be to shuffle things back around and throw a PCI SATA card in the TV box to get those drives working, but in the long run, and with the crazy-cheap prices on basic components these days, it’s probably better to build either a new TV box, or a new desktop.