The portability doesn't end with sata or usb ports.
With generic software raid (mdadm), even if you only had a single usb port and a single internal drive, you could image all the drives one at a time and then access the array of images on the single big drive. (not uncommon since usually time has passed by the time something fails)
It also goes the other way if you needed it to. Say a single array member was 4T but you only have a bunch of 1T drives, no problem, you can assemble 4 1T drives into a 4T container to hold the 4T image, and then use that image as an aray member itself.
Even if you don't have any loose external drives, you could even do it all via network shares with pieces residing on all of your other family members laptops and desktops, or every desk in an office, while they all still continue running windows and doing their normal jobs I mean.
Some of the possibilities are slow or fragile or both, so of course you don't set out to use 12 usb2.0 ports, but the point is essentially anything is possible, and you don't have to worry about predicting or planning for every possibility, you just don't have to care about how you'll recover the array in the future because it doesn't matter what form storage takes at that time, or what form you happen to have available. It would almost never make sense to do some things, but the point is that mdadm just doesn't care.
For a machine with only 2 or 4 internal drives where you want to use raid0 for max throughput, and don't want to rely on any special firmware support for booting raid0, just partition the drives so that /boot is a small raid1 across all the same drives, so that any of the drives could boot. Bonus, it automatically makes all the members of your main raid0 slightly smaller than the drive's nominal size, which means you can always fit them onto some other replacement drive later, even if the different manufacturers count bytes and formatting overhead differently.
I come from the days of sco unix on scsi hardware raid with full featured expensive cards and I do not miss it.