Seagate SkyHawk ST4000VX007 internal hard drive 3.5" 4000 GB Serial ATA III 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.