Thunderbolt vs. USB 3.0: Why it's a lose-lose

CNET editor Dong Ngo gives his take on Thunderbolt and USB 3.0.

The Promise Pegasus R6 Thunderbolt drive and the 1.5TB USB portable drive from Seagate.
The Promise Pegasus R6 Thunderbolt drive and the 1.5TB USB portable drive from Seagate. Dong Ngo/CNET

Ever since Intel announced Thunderbolt and made it exclusively available to Macs, Windows users have been wondering if they are missing out. The truth is: yes, they are, big-time. I've been working with the first Thunderbolt storage device, the Pegasus R6 from Promise, and find it to be the fastest consumer-grade storage device out there, period. (Stay tuned for my full review, coming up soon.)

On the other hand, since Macs generally don't support USB 3.0, which has been out for a long time and is becoming more and more popular in the PC world, Mac users have also been missing out quite a bit. Many people are wondering which is better, Thunderbolt or USB 3.0. This is a hard question, as Thunderbolt is about more than data storage; it's also about video transport, connectivity, expandability, and synced audio. However, strictly in terms of storage applications, neither is better. Consumers should really have both. The current separation of the two standards is a lose-lose situation for Windows and Mac users alike.

Here's why

Thunderbolt is slated to offer a speed of 10Gbps (which is about 1.2GBps). Real-world storage products generally offer much less than that, but still boast very fast data throughput. The Pegasus R6, for instance, is much faster than even a SATA 3 solid-state drive. And that's not a surprise, because the top speed of the SATA 3 standard, which is currently the fastest standard for an internal storage controller in a consumer-grade computer, is just 6Gbps (768MBps).

The Pegasus R6 hosts six SATA 3 internal hard drives. The reason it can achieve much faster throughput speeds than the standard (up to 800MBps as claimed by Promise) is because these drives are set up in RAID configurations that aggregate their individual throughput speeds into one combined speed that's much faster than that of each drive.

So for now, there's no point in making a Thunderbolt storage device that's made of just one internal drive. In this case its speed would be just the same as that of the internal drive, which is again 6Gbps or slower. Even in the case of the Pegasus R6, when connected to a Thunderbolt-enabled MacBook Pro, the transfer speed is basically that of the laptop's internal drive--much slower than what the external drive can do.

As it stands, unless you have a bunch of Pegasuses daisy-chained to one another and move data between them, you'll never get to see the drive's top speed when it comes to real-world data transferring. And that would be OK if investing in a Thunderbolt storage device wasn't a big deal, but it is. The cheapest version of the Pegasus R6 costs around $1,500. That raises the question: why should you invest in such an expensive storage device just to have its performance bogged down by your computer? Maybe because you don't have a choice.

Note that currently only the latest versions of the MacBook Pro, iMac, MacBook Air, Mac Mini, and Thunderbolt Display support Thunderbolt. While Thunderbolt is compatible with Apple's Mini DisplayPort (meaning you can host a Mini DisplayPort-compliant LCD via a Thunderbolt port), a Thunderbolt storage device won't work with existing Mini DisplayPorts.

On the other hand, USB 3.0 is slated to offer a speed of 5Gbps (640MBps), slightly slower than SATA 3 (6Gbps). This means you can use it to host just one internal drive without the drive being the bottleneck of the external storage device. And you don't have to worry that your computer's internal storage is the bottleneck, either, unless it runs a SATA 2-based drive.

In real-world testing, the sustained speed of a USB 3.0 external drive tops out at around 110MBps. Though this is for sure slower than a Thunderbolt device, anything that's more than 100MBps is plenty fast for most applications, even demanding ones.

The best thing about a USB 3.0 storage device is that you know for sure you'll get the most out of your investment, which is not much to begin with. A typical USB 3.0 external hard drive costs around $100 and offers terabytes of storage space. USB 3.0 storage devices can also be of any configuration, from portable to multiple volumes, as the device doesn't need RAID configuration to offer the top performance of the USB 3.0 standard.

That said, Apple's current lack of support for USB 3.0 means that Mac users have much more limited storage options and are forced to invest in a storage solution that is currently overkill in terms of performance and is, possibly, overpriced. It also just doesn't make sense that USB 3.0 is left out. After all, Mac computers already come with USB 2.0 ports, which have the same physical shape as USB 3.0, and USB 2.0 and 3.0 devices can be used interchangeably.

The lack of Thunderbolt in the PC world for now, on the other hand, means that PC users don't have access to an external storage technology that for the first time surpasses a computer's internal storage in terms of throughput speed. Hopefully this will change next year. For now, just in case you're wondering, installing Windows on the latest MacBook Pro (and the iMac) via Lion's Boot Camp won't provide support for Thunderbolt, either.

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