These pages provide basic information about how hard disk drives work.
Explanation Of Internal Hard Disk Components
The illustration shown above is a graphical depiction of a typical IDE based hard disk drive. Each component within this hard disk drive is explained in the subsequent table:
class="TableHeader" >Overview And Explanations Of All Hard Disk Drive Components
Overview And Explanation Of Purpose
This part of the hard drive works as a ventillation system that also prevents the bad air or particles from entering the drive unit.
spindle motor in the drive is responsible for spinning the platters
and these devices must be precisely controlled. They are set to
spin the platters at a fixed rate, usually ranging from 3600 RPM
(Rotations Per Minute) to 7200 RPM.
READ / WRITE HEAD
The read/write head as its name implies is the component that access data off a hard drive. The gap
between the platters makes room for the magnetic read/write head to perform its functions.
The read/write head works on the same principles as a floppy disk drive's read/write head but a much faster speed.
An IDE hard disk drive can have at least two or three platters also referred to as heads. Larger hard drives of course will have a larger quantiy of heads. The actual heads are comprised of an
aluminum alloy material or a mixture of glass and
ceramic material, covered with a special magnetic
The platters are typically stacked on top of
each other with a common spindle entitled a Head Actuator Arm used to "steer" the platters in the correct direction so that required data and files can be accessed properly. The platters normally contain a multitude amount of sectors or chunks. Each chunk can house a certain amount of data in the form of files and folders.
The head actuator turns the entire package of platters several thousand times per minute. The technical term for this is Rotations Per Minute (RPM). Most modern drives can spin the platters at 5400 RPM, while other high end hard drives (such as the ones located in server systems) spin at an incredibly fast 10,000 RPM. Laptop hard drives are typically slower drives spinning at 4200 RPM, although much faster drives are incorporated into newer, more expensive laptop computers.
VOICE COIL ACTUATOR
The voice coil actuator, is simply an electrical motor which moves or "steers" the head actuator arm.
MOLEX COMPATIBLE POWER CONNECTOR
The Molex power connector on all hard drives is a standard method for the drive to receive the neccessary power wattage to function correctly.
MASTER SLAVE JUMPER PINS
The pins situated in this area on any hard disk drive are used to control the chain of command of IDE devices within the computer. The chain of command simply refers to which device is set up in a master mode and which device is set up in slave mode.
The drive manufacturer normally dictates how a drive's jumper settings need to be configured, but all IDE hard drives follow a set standard for how the devices function within a system.
The basic principle of these settings normally include four sets of pins or "jumpers". Each jumper is controlled by a dip switch, which is a tiny black square shaped apparatus that when placed over a set of pins controls the master / slave designation.
An IDE hard drive can be configured in one of three ways: Master, Slave, or Cable Select. The table below illustrates how each method works.
Explanation of Mode
When a drive is setup to work in master mode, that hard drive has to be the first device which connects to the IDE cable. In other words, this hard drive working in master mode must be the first drive in the chain of command. Also, the second drive needs to be configured as slave so that the two can co-exist with each other on the same IDE cable.
When a hard drive is setup to work in slave mode, that hard drive needs to be the second drive that connects to the IDE cable. In other words, the hard drive working in slave mode must be the second drive in the chain of command. Also, in this mode the first drive connected to the IDE cable has to be configured to work in Master mode so that the two devices can co-exist with each other on the same IDE cable.
Cable Select (CS)
In Cable Select (CS) mode each device needs to be configured using the CS jumper setting on the particular device. In this mode, it is not neccessary for a two IDE devices to be referred to as Master or Slave devices, since all devices are communicating based on how the IDE cable connects the devices internally throught the system.
40 PIN IDE CONNECTOR
This 40 Pin IDE drive connector allows for the transmission of data between the hard drive and other components in the system. IDE is an older style technology but still remains in popular method for connecting IDE based devices to the motherboard's connections. A large number of workstations still implement IDE technologies since it is cost effective and is compatible with the majority of motherboards old-school and new. IDE devices are also referrred to as PATA (Parellel ATA); both terms reference the same style of hard drive technology.
HEAD ACTUATOR ARM
All disk platters in a hard drive are attached to the head actuator arm. This device actually directs the read / write heads as to where to move to access required data called by the Central Processing Unit (CPU). When the CPU calls for a particular sector of data, it locates the head, the track number, as well as the exact sector containing the data. It reads
this data from that particular section and sends it back to the processor for further calculation.
The time it takes for the head actuator to park the read/write head into the correct position
over a desired track is called the latency
period. The latency period is a common specification for measuring a hard drive's performance.
Table 1.1 - Explanation Of Hard Hard Disk Drive Components