External hard drives - Including portable and desktop devices.

external hard drive guide

External hard drives have become one of the most convenient devices to store large amounts of data. They are also invaluable for transferring data between two devices.

The storage capacity of external hard drives has increased dramatically over the past few years.

What is an external hard drive?

An external hard drive is the same type of hard drive as you would find inside a PC or laptop except that it is mounted in a separate enclosure. It can be used to store information (data) permanently or temporarily, in the same way as a computer's hard drive or a USB thumb drive.

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The actual drive itself comes in two main sizes (physical size), 2.5" and 3.5". The 2.5" drives are the same as you would find in a laptop computer, whereas the 3.5" drives are identical to hard drives found in desktop PCs. The difference is in the interface that connects the external hard drive to your computer.

Usually, external hard drives connect to the computer via a USB/Firewire cable, most modern operating systems will automatically recognise the hard drive as a storage device, and assign it a drive letter.

The fact that external hard drives are simply placed in an enclosure, means you can usually change the actual hard drive itself without too much effort. This allows you to swap drives between enclosures, so you only have to buy one enclosure for many drives (of the same type).

There are two main types of external hard drives, portable and desktop.

The portable external hard drive

portable external hard drive
Portable external hard drives are usually 2.5" hard drives (laptop hard drives) in a slimline enclosure making them easy to carry. Although they are portable they are not unbreakable and extra care is needed while transporting them, for example, don't put them in your back pocket and then sit down!

The portable external hard drive is commonly "USB Powered", which means you don't have to carry a separate power supply unit around with you. The only downside to this is that the available current (power) is limited to the computer it is attached to.

This may not seem like a big problem but if you have many other USB powered devices connected to the same computer (especially when connected to a laptop/notebook), then you will find the USB powered hard drive will not perform optimally.

Some of the portable external hard drives that are available come with a separate USB power cable which provides an extra power boost to the hard drive if required.

The desktop external hard drive

desktop external hard drive
Desktop external hard drives are normally 3.5" hard drives mounted in a larger enclosure than its portable counterpart. The enclosure may also have fans integrated to assist in keeping the drive cool during operation which helps extend the life of the disk drive.

The desktop external hard drive is designed with storage capacity in mind rather than portability. Common desktop hard drives boast 500GB of storage, which would have been unbelievable only a few years ago. In fact, the storage capacity of these drives currently go to 1TB (TeraByte) and above.

This type of external hard drive is still portable in a sense as you can still unplug and transport it. They often come with a separate power supply, which can be vital when you are transfering lots of data as it maintains a constant current, independant of the computer's USB power supply.

External hard drive jargon explained

When shopping for your new drive you will be confronted with drive-related jargon, below is an explanation of common terms used in the advertising of external hard drives.

Hard Drive Capacity: This figure, quoted in GB (Gigabytes) or TB (Terabytes), indicates the storage capacity of the hard drive. Your choice will depend on your requirements. As a guideline, a 160GB hard drive will hold over 40,000 MP3 songs or 133,000 digital photos.

Spindle Speed: This refers to the speed at which the drive rotates, the higher the speed the better. The speed will be stated in RPM (revolutions per minute), 5,400RPM is around the average speed of portable drives, whereas 7,200RPM (and above) is common in desktop hard drives.

Interface: This indicates how the hard drive is connected to the computer, usually USB and/or Firewire (IEEE 1394).
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