What Is A Computer Hard Drive

A computer hard drive is responsible for the storage of non-volatile data.  Non-Volatile refers to the hard drives ability to store Operating System files, program files, game files, and data files without the need for power.  When you turn off your computer, the hard drive retains the information, or data.  Many people confuse system memory with hard drive space.  System memory is Volatile.  This means data will be lost without supplying power to the memory modules.  Computer memory is only useful when your computer is powered. 

Computer Hard Drives store data on "Platters", or magnetic disks.  Depending on the size of the drive, it may have as few as 2, and as many as 5 Platters.  These Platters are 2.5" in diameter and are motor driven.  With the use of spindles, heads, circuit board controllers, and actuator, data can be stored and retrieved.  Although the ability to quickly store and retrieve large amounts of data in such a small space is very convenient, the speed of these moving parts make the Hard Drive one of the most fragile and likely computer parts to fail.  This is why backing up your data is vital. 

When the computer requests information from the hard drive, the controller is asked to find the data.  The operating system has already stored the location of this information within its registry.  So at this point, the controller simply needs to cross reference the data it needs to find with where on the Hard Drive it is stored.  Once this task is complete, the controller than calls the necessary heads to the location of the data.  Using the actuator arm, it can read the information from the platters.  The motor is responsible for spinning the platters at the correct speed.  Spinning the Platters is essential for data to be read and or stored.  This will not happen until the proper rotation speed is attained.  Once the data has been found and read, it is transferred to the controller cards buffer.  From the buffer, information is then sent to the Motherboard for further processing and handling.

Hard drives come in a variety of sizes and speeds.  Fitting your computer with a proper Hard Drive is based on Operating System, Programs, Games, and personal needs.  Programs that are large in size and demand require a faster Hard Drive with an appropriate storage capacity.  These specs are found on the box of the program you are buying.  It is important to think about the future and how much data you are going to store.  Hard Drives can be added and or replaced to suite individual needs. 

Common specs that should be considered when buying a hard drive is its Storage Capacity, Data Rate, Seek Time, RPM of Platters, Buffer Size, and cable connection.  Storage Capacity has been measured in Megabytes, Gigabytes, and Terabytes.   The Data Rate refers to the speed at which data can be supplied to the CPU (Central Processing Unit).  The rate is measured in bytes per second.  Seek time is how long it takes the first bit of information to reach the CPU after it is called for.  This is commonly measured in milliseconds.  Hard Drive Platters have 3 common speeds and one performance speed.  These speeds are measured in RPM (Rotations per Minute).  4200 rpm, 5400 rpm, and 7200 rpm are the more common speeds.  High performance Hard Drives are capable of spinning at a fast 10,000 rpm.  The faster the Platter spins, the faster information can be retrieved.  Although the faster a drive spins, the more likely it is to fail.  Buffer size is a huge advancement to Hard Drive Performance.  Buffers are a fast form of memory that the hard drive will write too before transferring it to the Motherboard.  The larger the Buffer capacity, the more data can be transferred within a given period of time.  This significantly increases the Hard Drives performance.  Common sizes are 2mb, 4mb, 8mb, 16mb, 32 mb, and even 64 mb.  How your Hard Drive connects to the Motherboard is another factor that affects the data transfer rate.  There are 3 main cable connections available today.  IDE/PATA cable is made from ribbon and has 40 pins.  These ribbon cables are capable of having 1 or 2 drives connected to it at the same time.  This allows for a single Hard Drive controller to operate 2 Drives.  This is the slowest of the 3.  SCSI is the next best performing ribbon interface.  With 70 pins, it is capable of controlling up to 16 hard drives.  SATA is today’s fastest interface.  Although only 1 drive can reside on a single cable. 

Hard drives have not changed much and remain the most vulnerable pc part in today’s computers.  With all the available backup solutions, hard drive failure should not be detrimental to your personal or business computing.  Hard drives are relatively inexpensive and easily replaceable.