If you’ve been browsing for a new laptop in recent months, chances are you’ve heard mention of a hard disk replacement technology called solid-state drive (SSD). Apple, for example, offers consumers the ability to swap out the traditional hard disk in its new MacBook Air for a 64-gigabyte solid-state drive. Similar options exist for many tablets, ultra-portables, and notebooks available from major Windows PC manufacturers, as well.

However, should you decide to exercise the solid-state drive option you’ll probably be adding between $800 and $1,000 to the price of the machine. The question, obviously, is why would anyone choose to spend so much money on something as mundane as storage? To answer that, we need to learn more about what a solid-state drive is.

Solid-state memory has been around for decades. It exists in several forms, ranging from ubiquitous RAM—short for Random Access Memory, the temporary memory found in almost all computational devices—to the flash cards used to store content in mobile phones and digital cameras to the embedded storage media used in some portable music players and camcorders.

The kind of solid-state technology typically used for solid-state drives in PCs is called NAND (a loose acronym for “Not and,” which describes the logical operation at work inside the drive). NAND storage has a significant advantage over other types of solid-state storage in that it is non-volatile, which means it can reliably retain information over long periods regardless of whether it’s connected to a power source.

All solid-state drives share one important distinction from hard disk drives: They have no moving parts. A solid-state drive is composed of billions of stationary crystalline cells, each of which contains a single instruction that can be turned on or off via an electrical charge. By contrast, traditional hard disk drives have platters that spin around thousands of times per minute as information is magnetically encoded on its disks with read/write heads.

This lack of moving parts is what provides solid-state with most of the advantages it enjoys over hard disk technology. No moving machinery means less wear and tear and no possibility of mechanical failure, which results in enhanced durability and security of data.

Jerome Kudera, an engineer and notebook product manager with Toshiba, a manufacturer of both hard disk and solid-state drives, explained that a mechanical drive can withstand an impact of only 0.5 gees before suffering damage caused by a read/write head crashing on its platter. By contrast, a solid-state drive can easily absorb shocks of up to 20 gees. Plus, solid-state drives can withstand and operate in extreme temperatures ranging from -25 to 85 degrees Celsius. As a result, it’s almost impossible to damage a solid-state drive under normal use.

Without moving parts, solid-state drives can also access data more efficiently, leading to a noticeable boost in performance. At the Consumer Electronics Show held in Las Vegas last month, Toshiba demonstrated how a computer equipped with a solid-state drive cut the amount of time required to load and boot up Windows Vista in a notebook from one minute to 30 seconds. PC manufacturer HP has conducted internal tests of its own that confirm solid-state’s performance advantage. Their experiments showed that an off-the-shelf HP notebook outfitted with a solid-state drive was able to access information more than 60 times faster than it did with a hard disk drive, and that it transferred more than twice as much data per second.

Of course, a performance increase of this kind won’t have a perceptible impact on everyday computer tasks that happen almost instantaneously already, such as accessing a Microsoft Word document or opening an Internet browser. However, it will be noticeable to users running applications that need to quickly access and transfer large amounts of information, such as video editing programs and high-end PC games. Rahul Sood, founder of Calgary-based luxury computer manufacturer VoodooPC, said that he expects gamers to be key early adopters of solid-state drive technology. "They’ve already entered the gaming space,” he noted.

Solid-state drives reduce energy usage, too. With no machinery to move, they have an active power consumption of just a single watt, as opposed to the nearly four watts sucked up by traditional hard disks. That means they run cooler, and, more importantly, have the potential to prolong battery life—a key selling feature for many portable PC consumers. Some manufacturers estimate that current laptops could operate up to 30 minutes longer per charge if their hard disks were replaced with solid-state drives.

The rest of the benefits offered by solid-state drive technology are likely to appeal to consumers’ aesthetic sensibilities. Depending on the capacity required, they are capable of being manufactured in dimensions that can potentially help decrease the thickness of some computer products, such as ultra-portable PCs. They may also help users take a load off—a 1.8-inch 128-gigabyte drive weighs less than 100 grams, whereas a hard disk of similar size and capacity tips the scales at around half a kilogram. And with no moving parts there’s nothing to make sound, resulting in zero acoustic noise.

The list of reasons why solid-state storage might be desirable is clearly long and varied. But it does have a couple of notable disadvantages: relatively small capacity and a prohibitive price.

The highest capacity model currently available that has dimensions compatible with existing hard disk bays is 128-gigabytes, but these drives cost several thousand dollars and aren’t yet offered as an option by most PC makers. At the moment, 64-gigabyte models that run around $1,000 represent the best value for reasonably substantial capacity. Still, these drives are hardly capacious enough to meet the needs of a consumer-based enamoured of large audio and video files.

However, according to solid-state drive manufacturer Samsung Semiconductor, 64-gigabytes will meet the needs of two-thirds of business users, who typically don’t load their work machines with multimedia files. Of course, there’s still the issue of price, but Jim Elliott, a spokesperson for Samsung, believes that some businesses are ready to pay a premium for durability and reliability. He thinks solid-state offers a value proposition similar to hybrid cars. “You pay a bit more up front for a hybrid, but you recoup that cost over time by paying less for gas and driving in the car pool lane to save time,” he explained. “Now, if you need to buy a thousand laptops for your company and factor in a five per cent failure rate for standard hard disk drives and lost productivity due to down time, solid-state might drop the failure rate enough to warrant the increased cost.”

Elliott also thinks that some non-business consumers will be willing to make the switch right away, stating that “Anyone who’s ever lost family pictures in a hard disk failure” might be willing to pay extra for solid-state’s enhanced reliability.

Plus, prices continue to drop even as solid-state density—which directly affects storage capacity—grows. “The density in the NAND space has been doubling every year for the last eight to ten years. We’ll be at a terabyte in a short time,” said Elliott.

Indeed, many PC companies are banking on solid-state drives slowly but surely replacing hard disks. HP’s Darren Leroux said his company already offers half a dozen notebooks and a tablet with a solid-state drive option, and pointed to forecasts produced by Gartner Research that suggest by 2010 roughly 20 per cent of notebooks sold worldwide will ship with solid-state drives.

But while solid-state drives may be destined to become commonplace in years to come, picking one up in 2008 will almost certainly leave a sizeable dent in your bank account. So, if you happen to be ordering a new notebook and see a checkbox to upgrade to a solid-state drive, best leave it blank and take comfort in the knowledge that, while you may be restricted to a hard disk drive for now, there’s a good chance that a solid-state drive will come standard in your next portable PC.