The potential uses of external and removable storage devices are as many and as varied as the people who use them. Here are just a few:
Replacing the hard drive in a desktop system is easy and inexpensive, but options for notebook systems are much more limited. Notebook hard drives are expensive, have relatively small capacities, and are slow. Adding an external hard drive to a notebook system addresses all of these problems. If the notebook has a USB 2.0, FireWire, or External SATA port, you can use one of the many models of external hard drives that support one or more of those interfaces. If your notebook has only slow USB 1.1 ports, you can install a USB 2.0, FireWire, or External SATA PC Card adapter to take advantage of the much higher transfer speeds of those interfaces.
If you need to transport or ship large amounts of data, an external or removable hard drive is often the best solution. External hard drives are available in very high capacities. A frame/carrier removable hard drive system uses standard hard drives, and so is limited in capacity only by the size of the largest standard hard drives available.
MOVIES ON DISK
For example, one of our readers works for a company that produces digital special effects for movies, always on very short deadlines. That company formerly used expensive, high-capacity tape drives to duplicate their 100 GB to 500 GB video sequences to multiple tapes and shipped the tapes to the movie production company. Nowadays, they just copy a video sequence to one FireWire external hard drive and FedEx the drive to the production company. When the drive arrives, the production company staff plugs it into a PC and copies the data from the external hard drive to a server. The external drives are so inexpensive compared to the value of the data on them that the drives are treated as consumables and are sent in duplicate to make sure that at least one copy arrives on time.
Software development and similar work that requires using multiple operating systems always presents a problem. You can configure one PC to multiboot different operating systems, but that is seldom entirely satisfactory. You can install a dedicated computer for each OS, but doing that is expensive, generates a lot of noise and heat, and means you're soon covered up in computers. Using a frame/carrier removable hard drive system solves all the problems. Installing each OS on its own hard drive means that you can simply insert the carrier with the appropriate OS, restart the system, and have the equivalent of a dedicated PC running that OS. We use frame/carrier units on our main test-bed systems for that reason.
Using a frame/carrier removable hard drive system allows one computer to be shared among several people. Inserting the drive and restarting the system presents each user with his own desktop environment, programs, and data, with no concerns about conflicts or accidentally damaging someone else's data or configuration.
One married couple with three teenagers reports that they used to have five PCs, all of which were getting old. They considered buying or building five new systems, but the configurations they wanted—fast video cards, large flat-panel displays, and so on would have cost more than they wanted to spend. Instead, they built only three new systems, each configured lavishly, and equipped each new system with a frame/carrier removable hard drive system. As it turned out, the couple ended up sharing one of the systems—he runs Linux and she runs Windows XP—while the three kids share the two other systems. Everyone is happier than they would have been with five inexpensive systems. (They also installed a gaming console, which keeps scheduling conflicts to a minimum.)
Some scientists, market researchers, and others need to manipulate extremely large data sets sometimes in the 250+ GB range. Although it may be possible to build a PC with sufficient disk space to store all the data sets on internal hard drives, it's usually cheaper and more efficient to swap those data sets in and out as needed. If there are many such data sets, using external or removable hard drives may be the only practical option.
Tape drives, optical drives, and other traditional backup solutions are too slow and have too little capacity to be practical for doing complete backups of today's huge hard drives. What's needed is something that's fast, stores a lot of data, and doesn't cost much per byte stored. In other words, a hard drive. In addition to their speed and capacity advantages, removable hard drives have a major advantage if you experience catastrophic system failure, because you can simply connect the backup hard drive and boot it directly, without spending the time needed to rebuild the system, reinstall the operating system and applications, and recover from tape.
Even the largest hard drive eventually fills up, particularly if you're a pack rat like Robert. External or removable hard drives allow you to store unlimited amounts of data offline. For example, one of our readers ripped his entire DVD movie collection to several external hard drives, and stored the original discs safely. Each external drive stores between 40 and 100 movies, depending on the capacity of the drive, the size of the movies, and the level of compression he used when ripping the movies. He keeps a rotating selection of two or three of these external hard drives plugged into his home-theater PC, and always has a selection of between 100 and 250 movies available for immediate viewing simply by choosing from a directory listing. If a movie he wants to view is on an offline drive, it takes only seconds to plug in that drive and access the movie. Others use external or removable hard drives for storing collections of music, digital images, or home videos. One person we know records an entire season of his favorite television programs, stores them to external hard drives, and watches them in a marathon session after the season has ended.
In olden days, the ubiquitous floppy disk was the medium of choice for sneakernetting data between systems that weren't networked. Nowadays, the 1.44 MB capacity of a standard floppy is ridiculously small, and even a writable CD or DVD disc may have too little capacity. USB 2.0 flash drives, which are available in capacities as large as 16 GB, and external or removable hard drives are capacious enough and fast enough to make it practical to transfer amounts of data that are impractical to transfer via optical disc.
If you work with extremely sensitive data such as payroll information using an external or removable hard drive allows you to secure that data by taking it with you or by storing it in a vault.
BEWARE TEMPORARY FILES
If you use an external or removable hard drive to store sensitive data, that drive must be bootable and should be the only hard drive in the system. If the external or removable hard drive is a secondary drive, the internal hard drive may retain temporary files, backup data files, OS swap files, and similar files that could compromise the security of your data. For absolute data security, configure the system without a permanent hard drive and always power down the system when you disconnect the external or removable hard drive. Also consider using good encryption (think AES) at the filesystem level for securing the data on a drive that may be vulnerable to theft or loss.
Advice from Jim Cooley
Portability is a key advantage of external and removable storage devices, but portability also means that these devices are easily misplaced or stolen. Always take steps to ensure that such devices are properly secured when unattended, and that the data on them is encrypted or otherwise protected against being accessed by unauthorized people.
Advice from Brian Jepson
You may want to look into TrueCrypt, an open source tool for creating encrypted images that can be mounted as drives. I use it on a laptop that came with XP Home, because encrypted NTFS files are supported only on Pro. I've grown extremely fond of it: http://www.truecrypt.org.
It's also survived numerous XP crashes (that weren't caused by TrueCrypt as best as I can tell) that happened while the virtual drive was mounted. In theory, I should dismount my TrueCrypt drive before launching a buggy game like Temple of Elemental Evil, but I forget sometimes.