The bMighty Blog -- Apple

Every so often, I’m asked this question by Mac owners: Which port should you use to connect an external hard drive, FireWire or USB 2.0?

In my experience, FireWire offers higher throughput than USB 2.0 for external hard drives, meaning that large file transfers go faster. It also seems to use fewer CPU and I/O bus resources, meaning that your overall system response time is affected less when you’re using an external FireWire drive.

For that reason, I deploy FireWire-based drives wherever possible. While external hard drives that have FireWire ports are usually slightly more expensive than those with USB 2.0 ports, I believe the performance difference is tangible and the extra cost is worthwhile.

This may seem contrary to the specs, since USB 2.0 is billed as having a bandwidth of 480 megabits per second, while FireWire 400 (the most common flavor) is rated only at 400 Mbit/sec. That is, slightly slower.

However, the numbers don’t tell the whole story. FireWire was designed for massive file transfers and for supporting high-bandwidth connections from external hard drives and video cameras. It uses a very efficient peer-to-peer architecture where two storage devices send data to each other without having to process all that data through a computer’s CPU. That added sophistication is why FireWire-based equipment can be more expensive, because each one needs its own microprocessor to manage the FireWire bus communications.

By contrast, your computer’s CPU has to manage communication across the USB 2.0 bus – which was originally designed for low bandwidth peripherals, like keyboards and mice, and only later extended to storage devices like hard disks, cameras and flash drives. This not only slows down the transfers, but slows down your computer.

The best place to notice the difference is when using a backup system like Apple’s Time Machine. When the Time Machine disk is a FireWire-based external hard drive, you barely notice when the backup starts. If you’re using a USB-based hard drive, you can feel the Mac slow down.

There are various “benchmarks” of FireWire vs. USB 2.0 all over the Internet. Most of the time, they don’t provide a lot of details about who ran the test, or exactly what was being tested. I’ve seen some word-for-word identical test results posted on many different sites, which makes me think that this is old data that’s probably out of context. Even so, I’ll share some of those numbers with you – without vouching for their veracity.

Here’s what a common set of Internet “benchmarks” claims:

Read Test:

• 5000 files (300 MB total): FireWire was 16% faster than USB 2.0
• 160 files (650 MB total): FireWire was 48% faster than USB 2.0

Even though the source of the data is unknown, it does square with my experience. So, I’ll stick with the advice to use FireWire for external hard drives whenever possible.

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