Computer Hard Drive Knowledge

A Computer Hard Drive is a form of Computer memory used to permanently store files and programs. Computer Hard Drives can also be referred to as; Hard Disk Drive. When using Microsoft windows a hard disk drive is often referred to as the c-drive. Most PC Hard Drives are stored in a internal drive bay at the front of the computer. Hard drives are connected inside the computer using a ATA, SATA or SCSI cable and a power cord.

There are several types of Hard Drives; some are IDE, SATA and SCSI:

1. IDE Hard Drive: (Also known as an ATA or PATA Hard Drive.) This is one of the most common drives used in computers. You can identify an IDE Hard Drive by having a 40 pin connector and a power connector.
2. SATA Hard Drive: (Also Known as Serial ATA). Very similar to an IDE Hard Drive but uses a higher speed. You can identify an SATA Hard disk by having a smaller power connector than IDE.
3. SCSI Hard Drive: SCSI Hard Drives are faster than IDE and SATA, but are more commonly used in servers due to higher cost. You can identify a SCSI Hard Disk at the connectors. (SCSI uses the same power connector as IDE.

There are four main components to a Hard Drive:

1. Platters: Aluminum, glass, or ceramic dishes coated with magnetic media. These dishes are used to store data and begin to rotate when the computer is turned on.
2. Head Arm: (Also known as a “Actuator Arm”) The Head Arm is similar to the arm on a record player. It allows the Hard Disk Drive to move the read / write heads to the location where the information needs to be read or written to.
3. Chassis: (Also known as the “Case”) A housing that helps protect and organize all components that make up the Hard Disk Drive.
4. Head Actuator: An electronic device controlled by a motor that moves the Head Arm to locations where it is needed.

 When looking to buy a hard drive you should be aware of some terms and specifications and what they mean:

Terms:	Example:	Definition:
Brand-	Western Digital	Name of Company supplying HD
Series-	Raptor	Category name within brand of HD
Model-	WD1500ADFD	Model Number of HD
interface-	SATA 1.5Gb/s	Cable connection between computer and HD
Capacity-	150GB	Size of HD storage
RPM-	10000 RPM	Speed at which data is transfered
Cache-	16MB	Small fast memory holding recently accessed data
Average Seek Time-	4.6ms	Time required for read/write heads to switch tracks
Average Latency-	2.99ms	Lapse of time between track switching and data access
Average Write Time-	5.2ms	Total time required to access data needed
Form Factor-	3.5"	Reference to size of disk diameters

Depending on a computers Motherboard setup and options it may be possible to run multiple hard drives. By doing this it is possible to run the drives in a Raid configuration. By running in a Raid configuration you can either have the hard drives working together to form one big hard drive, or they can have the data duplicated from one hard drive to another. By working together they are in a performace setup which allows one hard drive to perform task number one while the next hard disk is already onto task number two. In a duplicated mode each hard drive stores the same exact information so if one hard drive fails all of your information is still stored on the second drive. It is recommended when you replace your hard drive, you get one with more capacity than you would need right now so you will leave expansion room for the future.

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