Pen drives, thumb drives, jump drives, keychain drives... they're called many things and they use surprisingly varied technologies, but they all share a few features in common: They're compact, removable drives that attach to your PC via a USB port, and add anywhere from 16 Mbyte to more than 4 Gbyte of portable storage to your system.
In operation, they act much like an ordinary floppy or hard drive. Many of these devices are even bootable, if the PC is of recent-enough vintage to allow booting from a USB device. (Check your BIOS settings for Boot or USB options.)
Newer operating systems (XP, Win2K, and some Linux distributions) automatically recognize and mount these USB drives, assigning the next-available drive letter. Older operating systems (e.g., Win9x) may require a driver to recognize the USB device.
There are three main types of compact, portable USB-drives. The smaller-capacity variants tend to be sealed units about the size of a normal adult thumb--hence the common name: thumb drive. (One specific brand of this kind of drive goes by the trade name "ThumbDrive," but we're using the term generically--as in "thumb-sized drive.") These units have no moving parts, and emulate the operation of a disk drive via solid-state electronics and memory chips that retain data even when the power is removed.
The midrange variants are generally two-piece units consisting of a "media reader" device into which you can insert postage-stamp-sized memory chips; the electronics in the reader let the PC access the memory chip as if it were a hard drive.
The upper end units use no emulation: They are sealed or semi-sealed units that contain an actual miniaturized hard drive (see this example) that's also only the size of a postage stamp.
There's considerable overlap among these groups in terms of features and capacities, but each type of device is aimed at a specialized purpose. Let's take a closer look, starting with thumb drives, whose features serve as a foundation for all three types of devices:
Although the largest of the thumb-type drives have sufficient storage space to hold an entire operating system (and we'll come back to this later), they're much more commonly used to transport files and data from PC to PC. For example, you might simply copy all your most-important word-processing documents, spreadsheets, and such from your work PC to a thumb drive, carry it home in a pocket, and work on the files at home.
The larger-capacity thumb drives can even store an entire "My Documents" folder tree, making it possible to use one as your primary storage for those files. With your work and home PCs permanently set up to look for all "My Documents" files on the thumb drive, all you have to do is plug in the thumb drive, start the PC, and you'll instantly have all your My Documents files and settings available, no matter where you are.
Some thumb-drive users have found it helpful to move their browser Cookies, History, Cache, and other transient files to a larger-capacity thumb drive, too: This enhances their security and privacy because no traces of their work need be left on the PC they've used as everything of significance resides on the thumb drive. (See this for more information on moving these types of folders.) Once on the drive, these files can be encrypted or otherwise made snoop-resistant.
Thumb drives can be bootable, so they're also popular for diagnostic or repair work: Instead of having a toolbox of diagnostic and maintenance software on floppies or CD, you can place many of these tools on a thumb drive for fast and easy booting and repair work on any PC that supports USB booting.
Larger thumb drives, in the 128-Mbyte to 256-Mbyte range and up, also offer the prospect of holding a complete operating system, letting you carry everything--your operating system, its settings, your files, everything--right in your pocket. This can easily be done with any basic operating system that normally can boot from a floppy. For example, DOS and command-line Linux are a snap to get running on a bootable USB thumb drive. But it's harder with more complex operating systems that normally only expect to boot from a CD or hard drive; and that expect to "take over" USB support from the hardware. Windows in particular may start to boot fine from a USB device, only to fail when the operating system tries to take control of the already-running USB services. Getting a complete operating system on a USB device is a complex topic, and we'll devote an entire future article to it.
As for cost, at the time of this writing, the 256-Mbyte thumb drive seems to offer the most bang for the buck: A Froogle price search shows several vendors selling 256-Mbyte thumb drives at around $38, or 15 cents per megabyte. Smaller and larger capacities cost more per meg: 16-, 32-, 64-, and 128-Mbyte units, for example, cost 75 cents, 31 cents, 23 cents, and 18 cents per Mbyte, respectively; while 512-Mbyte, 1-Gbyte, and 2-Gbyte capacities cost 17 cents, 20 cents, and 23 cents per meg, respectively.
Of course, there are other factors to consider besides raw cost: Warranty, service, shipping, and ancillary software all can raise the value of a given product. For example, I purchased a 256-Mbyte thumb drive from Crucial for $49, or 19 cents/Mbyte. The Crucial unit is made of an exceptionally dense and rugged plastic that suggests extreme durability; the fit of the removable plug cover is extraordinarily smooth and firm, with none of the "click on" looseness I've seen in other units; Crucial includes software to hide and encrypt sensitive files you may place on the drive; and the device comes with a separate extension cable to allow easy use of the thumb drive on PCs that only have rear-mounted USB sockets. None of those features has anything to do with raw capacity, but they all affect and improve the overall usefulness and longevity. To me, these extras were worth a few extra dollars. But your choices are enormously varied, and you may decide that a different mix of features is right for you.
What I'm calling the midrange is actually an entire class of media-reading devices and their separate memory cards. These readers have a USB plug on one end and one or more open sockets on the other end designed to accept one or more media types: Compact Flash ("CF") memory, "MultiMedia cards," "Memory Sticks," "SmartMedia," "Secure Digital," and so on. These memory types are commonly used in digital cameras and some MP3 players.
The principal advantage of this approach is interoperability. A single memory card often can serve multiple purposes. For example, most cameras use an utterly conventional FAT-based file system for photo storage; PCs also use this format without trouble. This means the same memory card, stick, or chip can function for picture storage when used in your camera, but can function as a standard drive when attached to your PC. If you already have one or more memory cards for a camera or MP3 player, you can extend the usefulness of these cards with a low-cost reader, which typically runs $20-$30 or so for multipurpose readers, and even less for single-purpose readers.
The memory media prices for this type of application are roughly equivalent to the thumb drive prices previously discussed, so the overall cost--adding the cost of media and the reader together--makes this option slightly more expensive than the plain thumb drives. Plus, the two-part nature (card plus reader) means this approach is a bit clumsier to use. But if you're using multiple devices with external memory--cameras, MP3 players, etc.--adding a media reader to your PC may let you more easily use them all, and also give you the option of mixing and matching external memory to add thumb-drive-type functions to your PC.
Incredibly Tiny Hard Drives
These drives are amazing: Postage-stamp size, but containing the same parts and mechanisms as in your PC's full-sized drives: motors, heads, platters, interface ... the works. The platter is typically one inch (25mm) in diameter; the entire unit fits inside a Compact Flash Type II housing and weighs around half an ounce (15 grams). Typical capacities run from around 2 Gbytes to around 4 Gbytes.
The IBM/Hitachi Microdrive is probably the best-known brand, but there are actually a number of sources and vendors. Although prices change rapidly, as of this writing the "Magicstor" is the lowest-cost drive of this sort that I've found: a 2.2-Gbyte drive costs as little as $159; an astonishingly low 7 cents per Mbyte, or less than half the cost/Mbyte of the most cost-effective thumb drives.
These high-capacity small hard drives can normally be used as-is in any device that accepts CF type II memory cards, and that includes most of the low-cost media readers mentioned in the previous section. But you also can buy custom enclosures. For example, the Magicstor drive is sold by USModular, a reseller, with a compact plastic enclosure that doesn't affect the price much: the 2.2-Gbyte drive with a custom enclosure costs $195, which still works out to be under 9 cents/Mbyte. The enclosure makes the tiny hard drive as convenient as a thumb drive--the entire 2.2-Gbyte package easily slips into a pocket.
There are drawbacks to these small hard drives: Because these are electro-mechanical devices, they consume more power than the purely electronic drives, and may not be as well suited for battery-powered cameras, MP3 players, and the like. But for the applications where thumb-type drives are mostly used--carrying data from PC to PC--the extra power isn't an issue and the extra capacity is a boon.
The devices also can't be as rugged as a purely solid-state device, and they may encounter other mechanical limitations, too: For instance, some Microdrives have trouble operating at very high altitudes (over 10,000 feet/3,000 meters) because the reduced air density doesn't provide enough of a cushioning effect for the drive heads.
But overall, I found the Microdrive-type units to be quite agreeably hardy: For example, I've moved one while in active use, using only basic care (I didn't throw it), and had no trouble. In ordinary office use, I don't expect these drives to perform very differently at all from thumb-type drives. But in cases where very rough handling or environmental extremes are expected, these drives may not be the best choice.
Choosing Your Type
Standard thumb drives offer the lowest absolute cost, high ruggedness, and ease of use. They're also often the easiest USB drive type to make bootable. If you're on a budget or only need a modest capacity, you won't do better than a low-end thumb drive.
For a few dollars more--the $30-$40 range or so--you can hit the sweet spot and get around 256MB of storage in a well-made housing, with good add-on software and extras like extension cables. For most users, this is probably the best-available choice among all USB drive types.
For users who already have memory cards in cameras, MP3 players, and the like, adding a media reader/card reader may be a good alternative, allowing them to use their memory cards for PC data storage as well as the other uses, and vice versa.
For users seeking the highest capacities and lowest cost per megabyte in a thumb-like form factor, the Microdrive class of one-inch hard drive products simply can't be beat: If you need abundant add-on space for files, an operating system, or several CDs worth of repair/setup/diagnostic tools in a compact, highly portable USB device, this is the way to get it!
Later this summer, we'll look at ways to pare down an operating system so that it can fit comfortably in even a modest USB drive; and then later, we'll examine ways to actually set up your "OS on a stick." Stay tuned!
But for now: what's your experience with USB drives, external flash memory types, and Microdrives? What sources have you used to acquire the hardware and software? What tools do you use to format, manage, and maintain the drives? What boot tricks do you use? Let's pool our knowledge: Join in the discussion!