Some technologies just keep going and going. Despite the interest of vendors, customers, and analysts in flash memory drives and the move to better disk-space utilization, the use of hard disk drives (HDDs) continues to soar. In fact, according to IDC, 2005 represented a record year for HDD sales, both in terms of shipments and revenues.

IDC stated that global HDD unit shipments climbed to nearly 381 million drives last year, up a whopping 24.4 percent over 2004. And revenues hit the $27.9 billion mark in 2005, breaking the old revenue record of $27.8 billion in 1997.

Moreover, HDDs got both larger and smaller in 2005, IDC reported. Last year, 500GB HDDs began shipping, as did 0.85-inch form factor HDDs. But the tried and tested 3.5-inch form factor continued to be the most dominant.

The drivers behind HDD growth aren't hard to determine. PC sales, which are steadily climbing, continue to be the major force behind HDD sales. For example, in the first quarter of 2006, PC shipments jumped 12.9 percent year-over-year, according to IDC's Worldwide Quarterly PC Tracker surveys. Additionally, Gartner found that worldwide PC shipments climbed 13.1 percent in the first quarter of 2005 on a year-over-year basis. Interestingly, IDC analysts had projected a sharp drop of 15.9 percent in sales in the first quarter. Gartner analysts said that the results were in line with expectations.

Although strong PC sales mean strong HDD sales, sales are only part of the story. HDDs are being increasingly integrated into consumer electronics devices such as Apple Computer's iPod and digital video recorders. According to IDC, shipments of HDDs for use in consumer electronics will experience a compound annual growth rate of 23.7 percent from 2005 through 2010. In 2004, consumer electronics devices accounted for 15 percent of all hard drive sales. That number should ramp up considerably over the next three years, accounting for as much as 40 percent of all HDD shipments by 2008.

But perhaps most significant for the long term was the first shipment of perpendicular-recording hard drives in 2005. Perpendicular recording is a significant new technology that will enable HDD vendors to develop newer, faster drives with more capacity.

For the past 50 years--yes, the HDD is 50 years old--the disk-drive industry has used what's called a longitudinal-magnetic recording method. In this approach, the magnetization of each data bit is aligned horizontally with the drive's spinning platter. To increase the drive's capacity, vendors have concentrated on decreasing the size of the magnetic data bits and forcing them closer together, improving what's called the areal density. And the higher the areal density, the greater the capacity.

But the laws of physics have begun to limit the advances that can be made using longitudinal-magnetic recording methods. In a phenomenon called superparamagnetism, at some point, the data bits get so small that they lose their ability to hold their magnetic orientation at room temperature. If bits flip randomly, the stored data will be corrupted.

Perpendicular recording is a method to circumvent the limitations on longitudinal recording. In perpendicular recording, instead of the data bits lying horizontally, they stand vertically in relation to the spinning platter. Using this method, which was first proposed more than 100 years ago, vendors can still dramatically increase a drive's areal density without running into the effects of superparamagnetism. According to industry experts, by using perpendicular recording, a 3.5-inch hard disk with a storage capacity of 1TB could be developed by 2007. Last year, Hitachi Global Storage Technologies, Seagate Technology, Toshiba, and other vendors all released HDDs based on perpendicular recording technology.

However, the emergence of perpendicular recording has several implications. First, one of the unwritten rules of IT is that data grows to try and fill available space. And as hard drive capacities grow, more data and more different data types will be saved on HDDs. And this data will have to be managed and secured. Second, although it's now half a century old, HDD technology will continue to be a key storage component for as far as the eye can see