Hard Disk Drives (HDD's or Hard Drives for short) are a vitally important part of one's computer; they store all your information (programs, MP3's, work etc) on. Each computer system must have at least one Hard Drive, some have multiple drives. They can be both internal (inside the computer) and external (outside the computer). Hard Drives are the slowest part of one's computer. The size of a hard drive is measured in Gigabytes (GB). If you have lots of files it is worthwhile purchasing a larger drive.

There a few main types of Hard Drives available today:

SCSI - These are the fastest hard drives available. They are generally only used in servers and times where only the very best reliability is needed. These are also the most expensive. Speeds can be up to 320 MB/s.

SATA - This technology is relatively new. SATA drives are becoming the standard for desktop computers. SATA drives can achieve speeds of up to 375 MB/s. If you have an older computer you may need to purchase a converter card so your computer can use this technology. SATA can be used for both internal and external drives (providing the computer the drive is to be used on supports external SATA).

IDE (or PATA) - This technology has been used for many years. Most (if not all) systems in the last 15 years will support this technology. This type of Hard Drive is being replaced by the SATA drive. IDE hard drives can achieve speeds of up to 133MB/s.

USB/ Fire wire - These technologies are used for external hard drives. USB2 is the most common connection for an external drive. These drives are slower than the internal ones; the max speed for these types of drives is 60MB/s.

In addition to the type of hard drive it is also worth looking at the Spin Speed of the drive. These can vary from as slow as 4800RPM (usually for laptop hard drives) and to as fast as 15000RPM (usually for SCSI drives). The average speed is 7200RPM.

Cache size is also an important factor to consider. Usually hard drives have a cache of between 8MB and 16MB. The cache is where the data is stored before it is written to the hard disk. The cache is much faster than the drive itself.

The main manufactures for internal hard drives are Maxtor, Western Digital, Seagate and IBM. For external hard drives (in addition to those aforementioned) Freecom and LaCie.