Where does SATA fit in? I'm unclear on that concept.
SATA (Serial ATA) is the newest interface for hard disks. The old PATA (Parallel ATA) hard drives used the thin ribbon connectors and only got up to around 133 MHz (300 MBps, I believe?). SATA has transfer rates up to 5 GB/s, depending on the interface revision, and generally controls internal computer devices. However, SATA connectors are increasingly common for external hard disks, as it is plug-and-play or “hot swap” depending on the industry.
They were using SATA in the example, since hard disks will usually be the best indicators for read/write performance. External USB disks have been clunky and really only good for occasional archiving. FireWire was going to revolutionize that segment, but it never took off. USB 3.0 should be able to keep up with the newest SATA disks without issue.