Buying Guide - External Drives


An external drive or external HDD is a convenient back-up system for your data that is generally very easy to use.  An external drive can be kept separate from your computer, meaning that the external drive data can be used on any computer if and when this becomes necessary.

couple on laptopsAn external drive or external HDD can typically store far more data than most other domestic data storage systems, such as CD-ROM or the older technology floppy disk.  Unless you have a particularly large amount of data for storing on your external drive, you will be likely to need only the one external drive on which to periodically back up data from the main hard drive of your computer.  You could even use an external drive to back up data from a number of computers, making it a way of combining filing systems before transferring the data to a new computer.

Although there are different varieties of external drive, the most common types of external HDD for a domestic user will be the desktop external drive and the portable external drive.  As the names suggest, the difference between these two types of external HDD is essentially one of mobility: one external drive is designed to be kept in one place, attached to a computer via USB connection, while the other external drive is designed to be moved from one location to the next.  These can easily be carried in a bag for when you need to take your external HDD with you whilst on the move.  For an office situation with a number of interconnected computers, a network external drive is also available, so that the external drive or external HDD can be shared between the different computers on the office network.

Storage explained

The way in which your computer stores most of its data is via an internal hard drive, which is housed within either the desktop or the laptop computer.  The internal hard drive is used to store more permanent data, such as the operating system and any applications used regularly.  As a result, right from the start a good portion of your available storage space is taken up by your system's minimum requirements.  In addition, the system often builds up more and more data as it operates, from updating itself and carrying out antivirus checks, not to mention the growing number of documents that you will be likely create and save throughout the lifetime of the computer.

Modern user applications also use increasingly large amounts of storage space for the data that they produce, whether this is in the form of images, graphics, video, or highly formatted documents and other media.  All this means that the hard disk within your computer will fill up quickly, and if you have the same computer for a number of years, the accumulated data can become very substantial.

Solutions such as storage on a CD-ROM or floppy disk have been used for smaller segments of data, such as a selection of files or images, but to conveniently and reliably back up all your data from your computer, a storage space with a larger capacity is needed, and that is where the external drive or external HDD comes into play.

External drive or external HDD models are similar to the hard disk inside your computer, but with an external HDD, none of the operating system software or application files are required, as the external drive is usually run by your computer over a USB or FireWire interface.  In short, you are free to copy whatever data you need onto the external drive, and the external drive will not automatically fill up with system data.  Furthermore, as technology has advanced, external hard drive models on the market are able to store more and more data, meaning that it is even easier to make a full backup of all your personal data onto your external drive.


When you decide on the connection type between your computer and your external drive, you are likely to base this on the connection sockets that are already available on your computer.  Even so, if you want to use a connection of a specific type for your external drive it is often possible to have a port for this added to the circuit board on your machine.

hard driveTypically, however, your choice of connection type between your computer and your external drive will be between a USB interface and a FireWire interface.  It is likely that a modern computer will be fitted with a number of USB ports, so this choice is the safer option for your external drive or external HDD if you are uncertain of compatibility.  Even if you have an older computer with just one or two USB ports, it is possible to buy a USB hub, which is a fairly cheap way of splitting the USB connection, effectively providing you with several USB connections that you can use for your external drive, in the same way that you can purchase electrical extension cables for more than one electrical socket.

FireWire is a more recent type of connection and is convenient for extremely large files, such as long videos or large multimedia files, as the FireWire connection allows for a much faster data transfer rate.  Not all computers are necessarily fitted with a FireWire port however, so you should check this before you commit to a FireWire interface for your external drive.


In terms of the way that your external drive works, the main thing to look for apart from storage volume is rotation speed, as this shows the efficiency of external hard disks in the same way as for internal hard disks.  The higher the speed of the rotation of any external hard drive, the faster they can work to transfer data to and from the computer.

In general terms, the internal hard disk of a typical home computer is likely to have a rotation speed in the area of 7,200 rotations per minute (rpm), and that can act as your comparison point when looking at the rotation speed of an external HDD.  Other computers may have rotation speeds that are faster or slower, as may the external drive, but you certainly should try not to get an external drive with a rotation speed of less than 5,400 rpm, as this would almost certainly reduce the efficiency of the connection with your computer.

An external drive or external HDD rotation speed of more than 7,200 rpm, such as up to 10,000 rpm, is possible if you have a particular need for fast data transfer, but an external drive with this sort of rotation speed is also likely to have less memory space available for data storage.

With a regular external drive rotation speed, you can usually find a desktop external drive with a storage capacity of up to a terabyte of space (1,000 gigabytes), or a portable external drive with a storage capacity of up to 500 gigabytes.  Network external drive hard disks have greater storage capacities still, but domestic users will seldom require such capacity unless they have particularly great storage demands, for example, high definition video files or other media that require extremely large file sizes.