Hard disk drives are today’s fastest permanent storage media and have a large capacity. For this two reasons they are the most used storage medium in computers and servers. When buying a new hard disk, there are three important things to consider: – The connection of the disk to the computer or other device you will be using it with has a big influence on the speed with which data can be read from/written to the disk. Make sure the connection of the disk you buy is compatible with your computer! – The rotational speed is also important for the speed with which data can be read from/written to the disk and determines the time it takes to find a file on the disk. – Last but not least, the storage capacity of the disk, i.e. the amount of data that can be stored on the disk.