I also like the idea of having an easy homogeneous setup, each Pi having one disk, vs. my alternative (old PC parts) being something like '4 SATA ports on this one, and 6 on that one, but one's broken, less one on each for the boot disk' - I quite like the idea of having a bunch of Pis, and one image that I apply to all of them, which can include details like /dev/sda being its only data disk. That's not really a functional advantage, just appealing for keeping it simple to come back to and remember/understand how I set it up when I need to tweak something (and really easy to add another one increasing available cpu/ram/disk).