Comment by PragmaticPulp

> I wouldn't take a precious M.2 SSD slot on my main machine for 5-year old 1Tb drive, but I'd love to chuck 8 or 10 of them in some enclosure and build a nice performant NAS out of them. Alas, no such thing exists

NVMe M.2 drives can go into PCIe slots with an adapter.

If your motherboard supports bifurcation, you even put 4 x M.2 drives into a single x16 slot: https://www.amazon.com/Adapter-4x32Gbps-Individual-Indicator...

It wouldn't be difficult to find an older server motherboard with bifurcation support that could take 8 x M.2 drives with the right, cheap adapters. You'd have to read the manuals very carefully though.

The limit is the number of PCIe channels. ARM boards rarely have more than a couple lanes. You really need server-grade chips with a lot of I/O.

Or get one of the new cards with a PCIe Switch to connect 21 M.2 drives: https://www.apexstoragedesign.com/apexstoragex21