[dsr_]

Once upon a time the cool thing to do was to build RAIDs out of USB sticks. Or SD cards. Or floppy disk drives.

Raspberry Pi isn't as laughable as that, but the fact is that what you are getting out of this is a learning opportunity, not a reliable or high-capacity computing platform.

And even there, 4 Pi4Bs with 8GB will cost you $400 and more, once you add in power supplies and SD cards and desiderata. The first hit on Craigslist just now was a $200 4 core i7 with 8GB of RAM (upgradable) and a 256GB SSD in a nice small case. Two of those will get you better overall performance and leave room for expansion.