Firewire and USB – Speed isnt the whole story

It’s easy to survey the variety of connectors mounted on an external hard drive and be confused about which is the best choice. Most will have USB and Firewire, others may have USB, Firewire and Firewire800. Still others may carry a fourth option of eSATA.

All four of these run a different speeds but it would be a mistake to think that higher speed numbers mean by default better.

Standard Firewire has a speed of 400 mega bits per second (mbps). USB has a speed of 440mbps but this doesn’t tell the whole story. USB is a system administered protocol meaning that the actual speed that data will be moving fluxates depending on how hard your computer is working. Firewire by contrast is a bus speed that is largely operating system independent. The result is that whilst USB is technically faster than FW its speed can fluxate dramatically where as FW speed is generally quite consistent.

This has resulted in FW being the usual choice for video editors using external hard drives where consistency of the datarate is crucial to avoid issues such as dropped frames.

Firewire800 offers double the speed of FW(400) and logic might dictate that this equates to ‘twice as good’. Likewise eSATA which is faster again.

But there are other factors at work; most significantly is the hard drive speed. If you have a slow hard drive (measured in RPM) then a super fast connection like FW800 is superfluous – a bit like putting an old Datsun car on a F1 race track and expecting to go faster. The speed of the connection is only as fast as the speed of the drive.

External harddrives can vary in speed from slow 4200rpm (not good for media production but fine for word documents) through 5400rpm and 7200rpm which is the recommended minimum for production work. Higher end drives can spin at 10000rpm.

The actual speed of the data is dictated by the speed of the drive, the speed of the connection and the speed/performance of the computer and its OS altogether. A fast connection on a slow drive is not going to make the data move any faster.

So long and the short of it for short-form video production is that Firewire 400 is preferable to USB because of it’s more stable speed. Firewire already has a far greater bandwidth than formats like DV, HDV and XDCAM require. Firewire800 is overkill and you’re unlikely to see any difference in performance over FW400 unless you have a 10,000rpm drive. Similarly eSATA offers no real performance advantage over FW400 because the speed of the drive itself is the bottle neck.

That said, the bottom line is that all four of these are absolutely fine to use in most situations. If you are careful USB can work fine with no drop outs so long as your hard drive is reasonably fast, your computer is reasonably fast and you’re not running multiple applications at the same time.

On computers such as iMacs there is only one available Firewire port making capturing from DV/HDV via Firewire directly to a Firewire hard drive problematic. You can daisy-chain camera and hard drive together to use the same port but this has been known to cause problems particularly with FCP and JVC 201/251 cameras. In these situations connecting the hard drive via USB and the camera via Firewire is a quite viable solution. Once you have captured you can connect the hard drive back up via Firewire and edit away.