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FAQ: MacBook Air's solid-state disk

When it comes to storage, the newly unveiled MacBook Air offers an 80GB, 4,200rpm Parallel ATA hard drive as part of its standard configuration. However, that's not the only option - would-be MacBook Air buyers can also order the laptop with a 64GB solid-state drive (SSD).

The price for that downgrade in storage capacity: $999 on top of the $1,799 asking price in the US for the standard MacBook Air. So why would you pay so much more for less? Because, for some mobile users, solid-state storage is a compelling alternative to traditional hard drives.

MacBook Air: first look

Think of SSD as a grown-up version of those flash memory sticks you slip into your Mac's USB ports. Instead of storing data on spinning platters, as a standard hard drive does, SSDs store data in solid-state memory - either NAND flash memory or SDRAM. Increase that USB stick's capacity and add an ATA or SATA interface, and you've got an SSD.

SSDs seem like the perfect mass storage devices for a notebook. They have no moving parts, so they're less susceptible to damage from the shocks and jolts of travel. SSDs can withstand 10 times as much impact as a standard hard drive. They also deal well with vibration.

Then there's an SSD's parsimonious power consumption. Powered down, SSDs consume virtually no juice - somewhere around 0.05W. Even when operational, an SSD draws only 1w or so - about a third the consumption of a comparable hard drive.

In terms of seek times and throughput, SSD performance is about equal to that of a standard hard drive. But SSDs turn on instantly: They don't have to spin up platters as hard drives do, so they reduce computer boot, restart, and wake-up times substantially.

In addition to being sturdier, more power efficient, and faster than standard hard drives, SSDs are also slightly lighter and can, if necessary, be molded into different form factors to fit tight spaces. The circular platters of a hard drive don't allow for that kind of design flexibility.

So what's the catch? As the cost of the MacBook Air's storage option indicates, SSDs are still extremely expensive. However, there's some good news - the cost of NAND memory is declining by about 40 percent per year. In other words, what seems wildly expensive now may seem more reasonable in the not-too-distant future.


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