The age of the SSD is upon us

One of the most fascinating features of the new MacBook Air  Apples ultra-portable notebook computer, introduced at Macworld, and now shipping  is that its one of the first on the market to have a solid state disk (SSD).A SSD is like a hard drive, in that it holds gigabytes of data. Its like a hard drive, in that its persistent  that is, it remembers what it stores, without electrical power being applied to it, until you tell it to forget. However, unlike a hard drive, an SSD contains no moving parts. Instead, it has banks of special flash memory chips that can be programmed to act just like a hard drive.

Think of a SSD as being like one of those ubiquitous thumb drives, or the memory chip in your digital camera. Thats a perfect analogy: If you crack open a thumb drive or an SSD, youll find the same flash memory chips inside. A 64GB SSD, like the one in the MacBook Air, is really little more than a high-performance, high-reliability, 64GB thumb drive.

The main benefit of SSD today is that that theyre physically more durable than hard drives. Because there are no moving parts, theyre fairly indestructible. Dropping a thumb drive doesnt hurt it at all. Because SSDs dont use electromagnetic heads to read or write information, theyre unaffected by rogue magnetic fields (like, say, a big magnet). A notebook with an SSD can be knocked around more than one using a standard rotating hard drive. So, if youre traveling, youre less likely to see a hard drive failure one of the biggest problems with notebooks.

SSD technology  or specifically, flash memory technology  is making tremendous strides. The new 32GB iPod Touch, for example, uses flash chips. Just a year ago, that would have required a standard hard drive Sure, standard hard drives are bigger (the iPod Classic sports a 160GB 1.8-inch rotating hard drive), but flash is catching up.

So, yes, the age of the SSD is nearly upon us. Within a few years, flash-based SSDs will likely supplant standard rotating hard drives for many applications. But that eras not here yet, for most of us, for several reasons:

 Flash memory chips, like those inside the big 64GB SSD, draw too much power. Youd think that without moving parts, an SSD would be less electricity-hungry than a hard drive. So far, thats not the case the circuits draw a lot of juice. However, large flash chips are rapidly becoming more energy-efficient. So, theres no battery-life benefit yet.

 Flash memory is too slow. Depending on whose benchmarks you believe, a MacBook Air with an SSD is either slightly faster or slightly slower than the a MacBook Air with a standard hard drive. So, theres no performance benefit yet.

 Flash memory is too small. Right now, 64GB is the biggest youre going to find in a notebook SSD, though I expect that 128GB models arent too far away. By contrast, you can buy a standard notebook hard drive in sizes up to 320GB today. So, SSDs give you less storage than hard drives.

 Flash memory is too expensive. Compare the prices of the MacBook Air. The base model, with a 1.6GHz processor and an 80GB hard drive, costs $1,799. Swapping the standard hard dirve to a 64GB SSD adds a cool $999 to the price tag. Thats a heck of a premium. Part of that is economy of scale, to be sure. However, that making large-capacity flash chips is very expensive. So, flash memory is going to cost a bundle.

Within two years, we can expect to see a 4x shift in SSD technology: four times the size, four times the speed, maybe a quarter of the electrical power draw, and maybe a quarter of the price. Of course, in the mean time plain old hard drives wont be sitting still: theyre still evolving. But SSD is evolving faster.

So, your next laptop will likely still use a rotating hard drive, unless you have a special need for the more physically robust SSD technology. But the one after that you'll get a SSD, for sure.