External USB hard drives are the easiest way of taking your data with you. Unfortunately, many products restrict mobility because they require a large, bulky external power supply unit. Buffalo now offers a product that solves this problem with a much more elegant idea for powering its drives.
The obligatory external power supply is pretty much a necessity for external storage based on 3.5" hard drives, because those drives have a power draw that exceeds the 2.5 W that USB 2.0 can provide (500 mA at 5 V). Compact hard drives, however, do not necessarily require such high current. Many 2.5" external products can be powered by USB ; certainly, all 1.8" and 1" external hard drives can work without supplemental power.
Still, compact hard drives do not suit everybody’s requirements. Smaller disk platters mean less power is needed, but less storage is also provided. 1" hard drives are available at capacities of up to 8 GB ; 1.8" models store up to 60 GB ; and 2.5" drives feature capacities of up to 160 GB today. In the case of 2.5" drives, this is quite a bit of storage space, but it is far from the 500 GB of modern high-end 3.5" hard drives.
If maximum capacity isn’t your primary goal, then it is much easier to focus on mobility. We believe that 2.5" models are the best choice here, because they combine excellent performance and fairly high capacity. 1.8" drives are a bit smaller and lighter, but storage capacity and data transfer performance clearly suffer as a result.
Even if you go the 2.5" route, you would still be wise get a separate power supply unit if you want to be entirely sure that your hard drive operates with all USB host controllers. You’ll quickly notice that it is rather bulky and heavy, and this will cause you to stop carrying it, because you’ll usually not need it. Then, some day you will urgently need to use it on a particular machine and find it doesn’t work without external power.
Buffalo has a better idea. The company’s approach involves a simple buffer unit that is inserted between the external hard drive and the USB port.