A hard disk drive (HDD) stores digital data as magnetic variations on the surface of the disk. A bit (binary digit, the building block of all data within a PC) represents a 0 when magnetized in one orientation, and a 1 when magnetized in another.
Each individual disk inside a hard drive is called a platter, large HDDs contain several platters and use both sides of each platter for storage. The drive contains a motor that spins the platters at speeds from 5400 to 15,000 rotations per minute (rpm). Beside price, there are three main features that need to be considered when selecting a hard drive.
The three main features that determines the hard drive performance are spinning speed, capacity and type of interface.
The Speed of Hard Drives:
Basically, the faster a drive spins, the faster you can access and transfer data. Average access time of the hard drive and also Read and Write data transfer rate are the important factors of hard drive speed. Most of the best hard drives these days have a speed of 7200 rpm and transfer 100MB to 160MB of data per second. You dont want anything less than this, as you will notice annoying delays between reading and writing data. If you want a faster hard drive you can find drives with 10,000 rpm or 15,000 rpm, although you probably wont need such a drive for home computer use. The faster you go, the more you are going to pay.
Hard drives come in all different sizes, ranging from 40GB to 2TB. Purchase the largest hard drive you can afford. If you are going to store lots of data such as video games, music and video you might need a hard drive with 500GB capacity and more, so the size you choose all depends on what you need.
Hard Drive Interface:
The hard drive interface is the hardware that manages the exchange of data between a computer and the hard drive. The most common interfaces of hard drives are ATA (Advanced Technology Attachment) that comes in two forms, Parallel ATA (PATA) and the faster Serial ATA (SATA).There is also SCSI (Small Computer System Interface)/Serial Attached SCSI (SAS) drive which is mainly used on servers and high-end workstation PCs. SCSI is the fastest and consequently the best hard drive interface available, but its also considerably more expensive than SATA.
Noise and Heat:
Because the hard drive disk spins at high speeds, it produces noise and heat that can be annoying from time to time, this issue is particularly seen in older hard drives, however, some new hard drives still produce noticable noise level.