Computer storage is measured in bytes, kilobytes (KB), megabytes (MB), gigabytes (GB) and increasingly terabytes (TB). One byte is one character of information, and is comprised of eight bits (or eight digital 1’s or 0’s). Technically a kilobyte is 1024 bytes, a megabyte 1024 kilobytes, a gigabyte 1024 megabytes, and a terabyte 1024 gigabytes.


If a computer user is usually only going to create word processor documents and spreadsheets, then most of their files will probably be in the order of a few hundred KB or maybe occasionally a few MB in size.

If, however, a computer is being used to store and manipulate digital photographs, then average file sizes will be in the region of several MB in size (and potentially tens of MB if professional digital photography is being conducted). Yet another level of storage higher, if a computer is being used to edit and store video, individual file sizes will probably be measured in hundreds of MB or even a few GB. For example, an hour of DV format video footage consumes about 12GB of storage.

Non-compressed video requires even more space — for example:

2GB for every minute of standard definition footage, and 9.38GB for each minute of non-compressed 1920×1080 high definition video. Knowing what a computer is going to be used for (and of course many computers are used for a variety of purposes) is hence very important when planning storage requirements.


  • For many years 3.5″ hard disks have been standard for desktop computers and servers, and 2.5″ hard disks for laptops. Yet this is now starting to change, with enterprise class 2.5″ hard disks now increasingly being used in servers and some desktop computers due to their low power requirements. Indeed, the fact that Western Digital’s top-of-the-range Velociraptor hard drives now use a 2.5″ rather than a 3.5″ mechanism speaks volumes and probably indicates that within a few years most spinning hard disk drives are likely to be 2.5″.


  • The capacity of flash memory cards on the market currently ranges from 8MB to 64GB. There are also six major card formats, each with its own type of card slot. The most common format is the secure digital or SD card (see below). Next most popular are compact flash (CF) cards, which were the first popular format introduced, and which are used by many professional digital cameras and audio recorders. Finally come Sony’s Memory stick format (and not to be confused with a USB memory stick), the multi-media card (MMC) and the xD picture card (XD card).


  • Almost all optical storage involves the use of a 5″ disk from which data is read by a laser. Optical media can be read only (such as commercial software, music or movie disks), write-one, or rewritable, and currently exists in one of three basic formats. These are compact disk (CD), digital versatile disk (DVD)and Blu-Ray disk (BD). A fourth format called High-Definition DVD (HD DVD) is now dead-in-the-water.


  • Sometime in the second half of this decade, solid state drives are likely to replace spinning hard disks in most computers, with several manufacturers now offering hard-disk-replacement SSDs. These are often very fast indeed, extremely robust and use very little power. As pictured above, typically today most hard disk replacement SSDs are the same size — and hence a direct replacement for — a 2.5″ hard drive. They also usually connect via a SATA interface.


  • SD cards are as noted above the most popular flash memory cards now on the market, and come in so many variants that they do require some explanation. For a start, SD cards come in three physical sizes. These comprise standard-size SD cards (first developed in 1999), smaller mini SD cards (introduced on some mobile phones in 2003), and the even smaller micro SD cards. The latter were invented in 2005 and are becoming increasingly popular on smartphones and tablets. While the larger cards cannot fit in smaller card slots, adapters are available to enable micro and mini cards to be accessed by any device that accepts a standard-size card.


  • USB memory sticks (or USB memory keys, USB memory drives, or whatever you choose to call them!) are basically a combination of a flash memory card and a flash memory card reader in one handy and tiny package. Over the past five years, USB memory sticks have also become the dominant means of removable, re-writable portable data storage, and look set to remain so for some time. Not least this is because of their size, ever-increasing capacity (which currently ranges from about 512MB to 256GB), and perhaps most importantly their inherent durability.


Every major media has now gone digital, and as a result both companies and individuals are creating an increasing volume of data not just to initially store, but just as importantly to manage and back-up into a coherent archive. Indeed, in the film industry where the digital storage requirements for high-speed, random access archives can run into tens of terabytes on a major blockbuster, the job title of “data wrangler” has been born to signal the requirement for people to take on effective data management in order keep the production running effectively.

(With the decline of the Western, there has been a decline in the need for horse wranglers, though sadly the skill sets required for data wranglers and horse wranglers are not similar, with no former horse wrangler having been reported to have taken up residence in a data center).

Back with the typical computer user, the last few years have seen the death of the floppy disk (with its 1.44MB capacity), and for many the digitization of photography and their music collection. Video collections are also due to go the same way. Many if not the majority of households as well as businesses now therefore have many gigabytes of data that they really don’t want to lose. The devices and methods employed for keeping this data safe can be varied. And yet still, for some businesses and a great many individuals, the key storage issue to address is maintaining any level of suitable data backup at all.