Computer Hard Drive

Hard Disk Drive

Solid State Drive

Form Factor:

• The form factor of a hard drive is the actual physical size of the case the platters are in. The main sizes are 3.5inches for desktop and 2.5inches for laptop
• It doesn’t actually refer to the physical measurement of width or height of the drive, but refers to the size of the drive bay of the computer.

Disk Buffer:

• It is a small amount of memory, usually 8, 16, or 32MB, which is set aside for the most frequently accessed files. When one of these frequently used files is selected, it is retrieved from the buffer and this reduces access time since the system does not have to search the entire drive for the data. 
•  Again buffer, temporarily stores data while the data is the process of moving from one place to another, i.e. the input device to the output device

Interface Type

• The primary job of the hard disk controller or interface is to transmit and receive data to and from the drive.
• The different interface types limit how fast data can be moved from the drive to the system and offer different levels of performance
• The three main type of interface are
• Integrated Drive Electronics (IDE)
• Serial Advanced Technology Attachment (SATA)
• Small Computer Systems Interface( SCSI)

IDE (Integrated Drive Electronics):

• The IDE standard has been around for a very long time but as improvements were developed it later was called Enhanced IDE (EIDE) and even further developments brought about Advanced Technology Attachment (ATA).
• These drives connect to the motherboard via a flat, 40 or 80-wire cable to an IDE connector. It enables two drives to be attached on one cable.

IDE Cable

IDE

• The speed of a hard drive is determined by how fast the interface can send data. The primary drive rates between 100 MB/s and 133 MB/s with 133 MB/s being the maximum. These hard disks are commonly described by the abbreviation "ATA" followed by the speed of its connector (ATA 100, ATA 133). 
• IDE drive connectors use a parallel bus, meaning multiple bits are transmitted simultaneously. To distinguish between Serial ATA drives, IDE disks are also referred to as PATA (the "P" stands for parallel). 

Serial Advanced Technology Attachment (SATA):

• SATA disk drives are the current standard and use a serial interface to transfer data, i.e. data is transmitted one bit at a time which is faster than sending several bits at a time as with IDE.
• Data travels along a single wire, reducing interference hence one path is used for sending and another for receiving. 

SATA

• The original SATA standard had a transfer rate of 150 Mb/s (SATA-150).
• Now SATA can transmit up to 3 Gb/s (SATA 2), and 6 Gb/s (SATA 3).
• SATA uses a 7-wire cable for connecting to the motherboard.