Throughput Speeds for the Rest of Us

As I anticipate moving from my MacBook Pro to one of the new MacBooks, one of the things I have to consider is that I am losing not one but both Firewire ports. I have come to depend upon Firewire — also known as IEEE 1394 (1394a for Firewire 400 and 1394b for Firewire 800) — for moving data back and forth on hard drives. In particular, I use a small LaCie Rugged drive to hold my Lightroom library. It has a USB port on it, but I don’t know that I still have the necessary, and awkward, power bricked cord. Will I be able to use my Netgear network hard drive instead? Loyal readers of this log want to know, and so let’s do some math:

The table below lines up the protocol, its claimed throughput speeds in bits, and then a more realistic speed in megabytes. (As a reminder: there are 8 bits in 1 byte.)

table{border:1px solid black}.
|_. Protocol |_. Speed |_. In Use |
| USB | 12Mbps | n/a |
| USB2 | 480Mbps | 20-25 MBps |
| FW400 | 400Mbps | 40MBps |
| FW800 | 800Mbps | 80MBps |
| Ethernet[1] | 1000Mbps | 47 to 60 MBps |

The important difference between USB and FW is that the latter does not require a computer host port, and, I believe, it is capable of bidirectional traffic. Firewire ports can also carry enough power to support 2.5″ drives, which makes it extremely useful for moving large chunks of data by sneakernet. Newer iPods, however, can be powered off USB ports, and so I’m guessing that USB carries enough power for 1.8″ drives. (Time to down-size my portable drives, I guess.)

fn1. These speeds are based on using a wired ethernet connection to an Airport Extreme gigabit router hooked up to the Netgear ReadyNAS Duo drive unit which also has gigabit ethernet.