Hard drives
From TSG Library of Knowledge
A hard drive is used in computers to save information. A hard drive is comprised of a magnetic disc that rotates and is read by a head. Most computers have only one internal hard drive, but it is not uncommon to see an external hard drive used for additional storage or as a backup.
There are several styles of internal hard drives, varying in interface type, storage capacity, speed (RPM), and buffer size.
Contents |
Interface Types
IDE (aka Ultra ATA or PATA) , SCSI , SATA and SATA-II , SAS (Serial Attached SCSI)
Storage Capacity
A hard drive's capacity is usually measured in Gigabytes (GB), but also occasionally as GiB. Most new computers come with a hard drive of at least 100GB, which is more than enough for most computer users. Even so, it is not uncommon to see hard drives as big as 500GB in new computers, and drives up to 1.5TB, or terabyte are sold.
When comparing hard drive density, it is important to note the difference in which companies might market or recognize hard drive size. Manufacturers generally use the binary format, in which 1GB = 1 billion bytes (1,000,000,000 bytes) whereas Microsoft and other operating systems generally divide the space by bits, so 1GB is 1,073,741,824, and a 1GB rated hard drive will be reported as a roughly 930MB drive.
Speed (RPM)
In addition to capacity, hard drives are also rated by how quickly they can rotate the magnetic media. This is rated in Rotations Per Minute (RPM). Most desktop hard drives are 7200RPM, while most notebook hard drives are 5400RPM. High-end computers and servers usually have hard drives that run at 10,000RPM or 15,000RPM. Obviously, the higher the RPM, the better.
Buffer Size
Buffer size refers to memory built directly onto the hard drive for rapid access and storage. Common sizes range from 2MB to 16MB on modern drives. A Higher cache generally improves burst read/ write speeds.
Solid State Hard Drives
Unfortunately, because the hard drive has the only moving parts in the computer, it is also one of the most frequent to fail. A new technology, called Solid State, is a hard drive with no moving parts. It works similar to USB Flash Drives, which use memory chips rather than a moving magnetic media. There are some downsides to this new technology, including limitations to the number of reads and writes, but the biggest limitation today is that they are too expensive to be included in most computers. Apple's new light notebook, the Air, is one exception and is available with a Solid State Hard Drive.
Useful Software
Most hard drive manufacturers allow you to download software that allows you to clone your hard drive or check it for errors. A free program called HDD Health is available for Windows and will check your hard drive's SMART status and alert you if a failure is imminent.
