The latter are removable media that are tailor-made for transporting data from one machine to another. Hard drives on the other hand are the primary storage used by the processor to access and process data.

Hard drives store data on platters which have a magnetic surface. A read-and-write head hovering just a sub-micron height above the platters accesses this data. The platters are spun at a very fast speed by a spindle motor. The faster the platters spin, the quicker the data can be accessed by the operating system. Currently, the commonly available hard disks have a RPM (revolution per minute) of 5,400 and 7,200, though some manufacturers have launched drives of even 15,000 RPM.

Hard disks offer a phenomenal data storage capacity. Today’s desktop drives have capacities available in sizes of 80 GB, 120 GB, 160 GB and 240 GB. There are models with a capacity of 500 GB too. Hard drive manufacturer Seagate recently launched a hard disk with a staggering capacity of one terabyte.

Types of Hard Drives

There are many types of hard drives available in the market. These mainly differ in their interfaces. While buying a hard drive, you should get an idea about these interfaces and which one would fit your need.

IDE / EIDE (ATA) Drives
One of the prominent and very widely used hard drive interfaces is IDE or EIDE that stands for Enhanced Integrated Drive Electronics. It is quite easy to install and its data transfer speed is quite fast. Drives with EIDE interface are also called ATA (Advanced Technology Attachment) drives and connect to the motherboard with a wide ribbon cable. IDE drives are “parallel” drives, that is, they transfer data in many streams simultaneously to the processor. It is an old technology though and may disappear in a few years from now. SATA drives today look like the future.

SATA Drives
The acronym stands for Serial Advanced Technology Attachment. This is a new technology that makes hard drives extremely fast. The cable that connects to the motherboard is also quite thin compared to an ATA drive, thus decongesting the insides of the computer and leaving more room for airflow. These drives are “serial” drives because the SATA interface, as the name suggests, transfers data bit by bit at a time to the processor.

However, it does this so fast that its speed still comes out to be very high compared to IDE drives. If you have a choice and your mother-board can support them, always go for SATA hard drives, even if they are a bit more expensive than IDE drives. The extra money is worth it because of the high speed that the former offers. With SATA drives, the computer boots up quickly and software programmes also load in a less amount of time. This increases to your pleasure of using the machine.

SCSI Drives
These are the most expensive hard disks in the market today, coming for about three times the cost of ATA or SATA drives. They are very fast, in fact much faster than the latter two drives. However, SCSI drives are quite complex to set up on the computer as one has to tinker with the jumper settings. These drives are not very popular with ordinary desktop users (who are quite content with the performance of the SATA drives) but are used by high-end machines like Web servers.

Currently, ATA drives are the most popular in the desktop market, followed by SATA drives. SCSI drives come last for high-performance applications.

There are many companies today making hard drives all over the world. The most common brand names include IBM (now sold to Hitachi), Hitachi, Seagate, Fujitsu, Maxtor and Western Digital. Fujitsu and Seagate are well-known for making high-speed SCSI drives.

Hard disks are very delicate machines. They have many moving parts inside. The platters spin at a rate of 125 times a second. The read / write head is suspended less than a hair’s breadth above the spinning platters accessing the data. Obviously much can go wrong with this arrangement, though manufacturers try to make their hard drives as reliable as possible.

The biggest danger is a hard-disk crash. This occurs when the read / write head becomes unhinged and slams on the surface of the platters where it gets stuck. When you switch on the computer, it does not boot up. Instead, you hear a screeching noise from the disk. This means that the head is scratching the data-recording surface of the platters and destroying data permanently. You should immediately switch off the computer and call data recovery experts.