Lightning Strikes Twice


Q I see Thunderbolt becoming more common, but now I see a new Thunderbolt coming out. Is this like FireWire? My experience with going from FireWire to FireWire 800 wasn’t terrible, but not great. It all seemed to be about theoretical performance, but when I would use it, I wasn’t that impressed. Am I going to be disappointed again?
Via email

A I can understand why you’re a little wary of "theoretical" speeds. It was too easy to hear the name "FireWire 800" and think that you would be getting 800 megabits per second (Mb/s) transfer speeds (just like gigabit Ethernet isn’t giving you gigabit speed).

The lack of full-speed data transmission can be attributed to the overhead of the transport electronics (software controlling the transmission of data) and also the speed of the devices connected. There isn’t much you can do about the overhead, but if you connected a slow drive, the transfer speed also slows down.

New advancements in connectivity, like USB 3.0, Thunderbolt and Thunderbolt 2, however, are pushing transmission speeds (theoretical or not) where they need to be to deal with higher-resolution files like 4K.

Thunderbolt has a 10 Gb/s bandwidth across two channels, while Thunderbolt 2 allows those two channels to be combined to 20 Gb/s. Note that current Thunderbolt cables work with either version. For reference, USB 3.0 has a 5 Gb/s rate. At these higher transfer speeds, the gap between drive speed and connectivity speed takes on more significance. If you simply take a standard hard drive and connect via Thunderbolt, you’ll be underwhelmed at the speed. Even some of the first "Thunderbolt" drives on the market didn’t have the speed to fully saturate the Thunderbolt bus, so while performance was improved, it wasn’t what one might have been expecting.

Drive manufacturers striving to increase drive speed to work with high-performance connections like Thunderbolt currently have the following options: put multiple drives together in one system or use solid-state drives (SSDs). In some cases, they do both.

I recently had the opportunity to see an example of "doing both" with a demonstration of the LaCie Little Big Disk Thunderbolt 2 connected to a new Mac Pro. This device uses a pair of SSDs to serve up the data. Running a simple speed test on large video files showed speeds approaching 1,300 MB/s (megabytes) or 10,400 Mb/s. That’s very close to the specified bandwidth. In addition, when you take two of these drives and connect them each to a separate Thunderbolt controller on the Mac Pro, and then create a striped array using the built-in software of the Mac, the speed approaches 2,400 MB/s. For transferring 4K data, those speeds really have an impact.