Portable hard drives are great devices for storing files and backing up your data, but there are a few "gotchas" that you should be aware of if you use one of these devices.
As we accumulate USB devices like printers, scanners, webcams, and microphones, we often run out of USB plugs on our computer. The solution is to use a USB hub, a small device called that can create multiple USB ports from one outlet on your computer.
However, there is a problem that often occurs with portable USB hard drives and USB hubs. Regular USB hubs draw their power from the USB port on the computer. A portable hard drive requires more power than it can get from a regular USB hub. So when a hard drive is attached to a USB hub it may not function properly. Sometimes plugging the hard drive into a USB hub will cause erratic behavior that is difficult to trouble-shoot.
The solution is to always plug a USB hard drive directly into the computer's USB port. While most USB hubs are not self-powered, you can find some good USB hubs that have their own power meaning that they come with a power cable that can be plugged into the wall. If you must plug a USB hard drive into a USB hub, purchase a good powered hub that can give the hard drive the power that it needs to run correctly.