The recent release of Apple's iPod nano and its use of flash memory instead of a hard disk signals what promises to be a tectonic shift in storage over the next several years. Taking a long view, even with all the advances in storage capacity and management capabilities over the years, storage media itself doesn't change all that often. Since the beginning of computing, storage has evolved from tape to floppy disks to hard disks, with optical media used for certain specific applications. Since hard drives emerged as the dominant storage medium, the major technological advances have been in capacity, speed, form factor, and, of course, cost.

Increased hard-drive storage capacity at reduced costs has been one of the major enabling technologies of computing as we know it. This capacity has allowed application software to become more complex and is the repository for many of the terabytes of the data currently being generated and stored. But in years to come, in personal computing devices such as PCs, flash will be a formidable competitor to hard-drive technology.

The use of flash memory has exploded through the emergence of digital cameras and MP3 players. It's being incorporated into cell phones and a wide array of other consumer electronics devices. The mass market for flash has led to an extremely aggressive development trajectory and rapidly falling prices. Samsung, one of the major flash vendors, has announced a 16GB flash unit. With analysts projecting flash capacities to double yearly, within 2 years 64GB flash memory should be available. And 64GB represents quite a bit of storage, even in today's data-saturated environment. By 2007 or 2008, flash with 128GB capacity should be ready.

Although it's more costly per gigabyte than hard drives, flash has some key advantages. First, since it isn't a mechanical device, flash is less prone to failure. For many PC users, the hard drive represents the key point of failure in their systems. They'll find a more-reliable storage medium very attractive.

Second, flash uses less power, and power consumption has become a key design criteria at almost every level of computing. Finally, flash memory takes up less space. The iPod nano demonstrates consumers' love for that sleeker and more elegant design that a smaller storage device enables.

Flash memory is developing quickly, but hard-drive technology isn't standing still. Hard-drive manufacturers are optimistic about a new technology called perpendicular magnetic recording (PMR) that could exponentially increase hard-drive capacity. Seagate Technology and Hitachi Global Storage have signaled their intention to introduce 2.5-inch PMR drives aimed at the notebook market.

Moreover, research from Current Analysis shows a marked increase in the sales of 100GB and 250GB hard drives in the US PC market over the last couple of months. According to Current Analysis, 250GB hard drives now represent more than 10 percent of the market, while 100GB drives account for nearly 20 percent of the market, just a few percentage points less than the most prevalent 80GB drives.

What does it all mean? First, it seems clear that flash will increasingly find its way into personal computing devices. The potential benefits of increased reliability, lower power consumption, and improved design will be more compelling than the drawbacks of somewhat smaller storage capacities and perhaps some additional costs.

Second, flash's smaller storage capacity could lead organizations large and small to encourage their users to store more of their information on large shared disks. Overall, this could be a positive development, giving central administrators more control over backup and other computing best practices that individual users too often ignore.

On the other hand, as users become more comfortable with flash, they'll increasingly use portable pen or thumb drives to take their data with them, giving administrators less control over what might be valuable data.

The increasing use of flash memory for storage should have a major impact on companies' storage infrastructure over the next 2 to 3 years. But if administrators don't monitor flash developments now, before they know it, users could be walking around with large amounts of sensitive data on unsecured flash drives as they adjust to having more constrained local storage on the desktop