Today's computers can process a huge amount of data in a matter of minutes. They therefore need a readily accessible data bank at their beck and call. There is only one storage device that fits the bill for this purpose ? hard drives. They have for decades been the primary storage for all computers and laptops.

Hard disks are screwed inside computers and laptops. They are connected to the motherboard through data cable and derive power from SMPS. These drives are a very complex piece of machinery, a true marvel of modern engineering.

The exterior of hard disks is made of metal to shield it from trauma and shocks. Inside, the main component is a series of metal platters arranged in a vertical stack. This entire assembly rests on a spindle motor. The surface of the platters carries a shiny but thin coat of magnetic paint. This is the actual data-recording area.

For each platter, there is a read / write head that hovers above. Situated at the end of an actuator arm, this head carries an electro-magnet that does the actual work of accessing, reading, writing, modifying and deleting the data. The disk controller card acts as a go-between with the operating system, while the circuit board regulates the power supply to the various components of the disk.

When the hard disk is switched on, the motor spins the platters at a speed of about 150 revolutions per minute (RPM) or more. The actuator arm moves over the platters from its parking bay and the read / write head starts accessing the data as per the requirements of the operating system.

Whenever you switch off your computer, it is essential for you to shut it down properly through the operating system. This gives the read / write head enough time to disengage and move to its resting place in the parking bay.

If you shut down the computer abruptly through the power switch, the actuator arm will come to rest on the platter surface. When you boot up the machine later, the platters would start spinning and the read / write head will end up scratching the platter surface before it can lift itself up, thus causing bad sectors and data damage.

Hard drives that are made portable are called external hard drives. These exist independent of computers but can be connected to them through high-speed USB data cables. External drives are made rugged and sturdy because they are meant to be carried from one digital device to another. They cost about twice more than regular hard disks and come with a software that automatically takes backup at regular intervals from any computer or laptop.

External hard drives have many advantages. The first and foremost is that they are small and independent units that can be easily ported. Indeed, many models are smaller than your palm and can easily fit inside your shirt pocket. The other phenomenal advantage is their capacity. No other portable storage device currently comes near external drives which have a capacity ranging from 80 GB to 240 GB.

Unlike tape drives (also a common portable media for taking backups), portable hard drives offer random data access. This is a big advantage if you have to access a single file as it can be retrieved instantly, no matter where on the platter surface it is residing.

The main disadvantage of portable hard disk is its susceptibility to physical trauma. If it gets dropped by the user to the ground, it can suffer serious hardware damage and has to be taken to a professional data recovery company. Also, compared to other portable storage media, a portable disk is expensive.

These disks can lose their data in various ways, in addition to the previously managed impact trauma. There are many sensitive and delicate components inside a hard disk and any of them can go wrong. The

most serious case is when the read / write head comes crashing down on the platter surface and gets jammed there.

When the platters spin, the head scratches the data-recording area, causing permanent data damage. Another common cause of data loss is the spindle motor that may stop working. Sometimes, the controller card or circuit board get fried due to an electric surge.

There are software errors too, such as reformatting of the hard disk which makes all previous data invisible to the operating system. Software corruption, accidental deletion of a file and virus attack are other causes of data loss from a portable hard drive.