External hard drives are cheap these days, but they are also fragile. Spill coffee on them or set fire to them (bear with us) and the chances are you'll have real trouble - and expense - recovering any of your valuable data without expensive forensic help.

The same applies to data stored on laptops or even desktop PCs. In the event of fire or flood, you can almost certainly kiss goodbye to the files and information stored on the hard drive. If this data is your MP3 collection or photo album, that's a real shame. But if it's your company accounts and contact database, it could mean the end of your business.

Some individuals and companies choose to mitigate against disasters by using online backup services to store their data off-site. This certainly has its advantages, but for people who prefer to keep their data local, how do you ensure that it can't be destroyed? Fires and floods happen, and your average PC or external hard drive wasn't built to survive them.

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The Solo drive from ioSafe is one possible answer. It's not often we review external hard drives weighing more than a desktop PC, but at nearly 7kg, that's what we have here. There's a reason for the bulk, though: inside this USB-connecting case is a lot more than just a hard drive.

Currently available in 500GB, 1TB and 1.5TB capacities, the 500GB unit we reviewed was easy to install; just attach the external power supply brick and plug in the USB cable. Formatted as NTFS, it's immediately recognised by Windows XP and Vista, while Mac users can reformat it to suit their OS. There's a cooling fan but it makes no more noise than that of a standard desktop PC, and isn't intrusive.

LEDs on the front of the case let you know that the device is working, and are quite pretty if you like that sort of thing. There's a hole at the back for securing the drive to a desk with a cable or bolt, and the grey metal casing, while not exactly stylish, isn't going to do too much aesthetic harm to your working environment.

In day to day use that's all you'll really notice, but inside the case are some clever technologies designed to keep your data safe in the event of disaster. First, the drive is fireproof to 840 degrees C for half an hour, which should give your data a fighting chance of survival in the event that the unthinkable happens and your home or office burns down. Second, it's waterproof, to 10 feet of fresh water or salt water for three full days.

You may wonder how this is all possible given the cooling fan and airflow, but the ioSafe Solo has some clever tricks that close down the cooling vents in the event of fire, and also release moisture from the embedded insulation to help keep the temperature down, while maintaining a waterproof barrier around the hard drive unit itself.

We didn't test these claims to destruction ourselves, but others have done with positive results, and ioSafe backs its product with a three-year warranty and a £500 data recovery service included in the price of the drive.

Comparing the price of this unit with the price of a standard external USB drive, the small additional price could provide you with considerable reassurance that your data is safe in the event of fire or flood.