Would this work? Storage Device, SSD, 8PB for cheap?

[Recursion]

6. Finite writes make this a problem, and you'll need a logical filesystem that will be a PITA

You can only write to an SD a certain number of times before it goes kablooie. Now, you could have LEDs like RAID arrays do to show you which one to replace. But that gets to another point: what kind of redundancy do you want? RAID 6? 1+0? Something else? Write times and seek times are going to be problematic, and since the filesystem metadata and block map will have to be either in memory or on a faster filesystem, that's going to add a ton of complexity. That said, if you build one, I'll write the filesystem for it. That sounds fun.