Product Survey: External Hard Drives

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Whether you've just run out of space or want to finally want to get round to sorting out regular back-ups for your data, then adding an external drive is an attractive solution. There's nothing to take apart and nothing to put back together again: just plug it in and off you go!

Pierre-Jean Alzieu
Updated: January 14, 2010

Our Tests

For external hard drives, we've stuck to a series of practical tests that we time by hand. We use two batches of files: a few hundred MP3s on the one hand, and a single huge video file of 6.4 GB, and copy them onto and then back off the drive to measure average read and write speeds.

On our test PC, we've got a pair of super-fast Western Digital 36 GB Raptors turning at 10 000 rpm in a RAID array--a set-up that's easily faster than any of the external drives we test and therefore unable to hold back their performance.

We do the same series of tests using each one of the connectors available. In practice that means USB 2.0 in almost every case, and then one of either eSATA or FireWire 400, depending on which standards the drive supports.

If you want to keep a reliable backup of your data without piling up the CDs and DVDs--or have just run out of space elsewhere--you've got two options:

the DIY approach: you can get a screwdriver out and either add a new hard drive inside your computer or install a hard drive in an enclosure
the easy way out: choose an external hard drive like the ones in these tests.

Prices haven't really fallen that much in the past year, and going for a large external hard drive shouldn't cost much more than £100. What has changed, though, is the amount of storage you get for your money: the current generation of 500 GB drives are great for keeping track on your collection of thousands of photos and videos.

Speeds: 30 MB/s over USB, and up to 80 MB/s over eSATA

Speeds have also been improving, mostly because of the growing popularity of two standards that used to be reserved for professionals: FireWire and eSATA. Some of the disks we tested reached speeds of 80 MB/s, meaning you'll only need a minute to copy the equivalent of an entire DVD: 4.5 GB. That renders DVD burners largely useless--and they're a lot more expensive, too.

Checking how fast a hard drive can copy data is one thing, but it's not the only important factor. Some other questions you should ask yourself include: 'is it quiet?', 'do I like the design?' and 'what's the power consumption like?'. To help you find the answers to these questions, we measure noise levels, both with and without 'silent' mode (AAM) when it's available as well as energy consumption.