The main reason for buying a hard drive is to provide sufficient storage capacity, but there are other reasons as well. Since hard drives have a very noticeable influence on performance, getting a fast drive is important for anyone who remotely cares about a good performance experience. Users seeking a large capacity drive can focus on a good cost-per-gigabyte ratio. Here is a list of reasons why you might want a new hard drive:

1. Add an additional hard drive
2. • to provide more storage capacity
   • to provide backup storage capacity
3. Replace the system hard drive
4. • by a drive with larger storage capacity
   • by a faster drive
   • by a drive that is faster and provides more storage capacity
5. Buy a hard drive to install in an HDD enclosure, or buy an external hard drive, which is semi-portable (3.5" products) or portable (based on 2.5" drives or smaller models)

Purchasing additional hard drives for backup purposes has become increasingly popular. On the one hand, hard drive capacity is very affordable at almost a quarter per gigabyte. On the other hand, handling data on a hard drive is convenient, as hard disks offer both high capacity and high performance. Also, the Serial ATA interface is fast and can be used very flexibly today, both internally (SATA) or externally (eSATA).

Tape backup solutions may be more reliable, but require backup software and more planning. It's not possible to restore tape backups without an appropriate streamer.

Recordable DVDs are another approach for backups, as drives are incredibly inexpensive and media is easy to handle and can be read with any DVD drive. However, DVDs only store 4.7 GB on single layer discs or 8.5 GB on double layer media. If you want to backup dozens of gigabytes, you will end up spending a couple hours doing so.

Finally, you can also look for NAS storage devices, which will provide plenty of storage capacity within your local network. But since NAS products are mostly based on hard drives (and sometimes RAID technology), they are simply an extension of hard drive storage media solutions.

3.5" Desktop Hard Drives

Standard hard drives for desktop computers utilize the 3.5" form factor, which refers to the width of the drive. There are models with UltraATA interface or Serial ATA. The latter is more advanced, offers better bandwidth and is much easier to add to your PC, as you do not have to configure the hard drives. Two UltraATA drives have to share one port (referred to as channels), while one serves as a so-called master drive and the other as a slave drive, which is defined by setting a jumper on the hard drive.

3.5" hard drives are available at capacities between 40 GB and one terabyte. Performance is determined by the recording technology and the rotation speed, but it is safe to say that the current product generations are clearly faster than their predecessors. For more information, please have a look at our article "Understanding Hard Drive Performance".