Hard Disk vs. SSD: What's the Difference?

With the MacBook Air's arrival, Solid State Drives, or SSDs, seem to be making a run for the mainstream. (Numerous other vendors, including Dell and Fujitsu, sell them preloaded in laptops.) But many look at the extra thousand bucks or so that an SSD costs vs. an old-school hard drive and wonder.... um, is this really worth it? What is an SSD anyway? Well, I've heard the question enough times now that it's time to answer it in depth.

What is an SSD? A solid state drive is designed to act just like a hard drive as far as the user or the computer is concerned (and even looks similar on the outside), but it has no moving parts. SSDs have no spinning platters; instead they are based on flash memory, the same stuff in a camera memory card or a USB thumbdrive. Only there's lots more of it: Most SSDs are now 32GB or 64GB in size. That's a lot of flash memory.

SSDs are faster than hard drives (up to hundreds of times faster), use less power, and weigh less than traditional spinning hard drives. They don't crash when you drop them, and they don't make any noise. Over time, we should see far greater capacities in the same amount of physical space, too. Sounds great so far. But there's one catch: Magnetic hard drive technology is dirt cheap. Flash memory is very expensive. 64GB of hard drive space would cost you less than $50 (if you could even find a new drive that small). 64GB in SSD format? At least $1,000.

And there's the rub. All of flash's advantages are obviated if they double the total cost of your computer. Many people look at SSD drives and say, Hey, I'm accident-prone, and my drive won't crash if I drop the laptop... so maybe I should get an SSD. Well, maybe... but you could actually replace any broken hard drive for $100 or so. And you're making your backups, right? Is the SSD's insurance really worth 10 times the price of a spare hard disk?

In time, SSDs will probably completely replace hard drives in many applications, especially notebooks, but for now, they're really just a luxury toy for the ultra-rich who want a quieter, lighter, and more ghastly expensive laptop. Give it four years, then ask me again. For now: Just get a hard drive.