Apple will sell you a laptop this month with a sixty-four gigabyte solid-state disk instead of a hard drive. The option costs about a thousand dollars on its own, which is more than a lot of complete computers, for less than half the capacity of the drive it replaces.
Nobody sensible should buy that configuration. It is still the most interesting thing in the machine.
The reviews will benchmark it wrongly. They will run a large file copy, report a sequential transfer rate, note that it is somewhat faster than a good laptop drive but not dramatically so, and conclude that the price is indefensible. The sequential number is the one benchmark where flash currently has the least advantage, and it is the one everybody runs because it is easy and it produces a big clean figure.
The number that matters is the one nobody puts in the table. A mechanical drive has to physically move a head to reach a piece of data, and that takes somewhere around ten milliseconds, every time, no matter how fast the platter spins. Flash has no head. Access time is measured in fractions of a millisecond and it does not care where on the chip the data is.
Almost everything that makes a computer feel slow is random access, not throughput. Booting is thousands of small scattered reads. Launching an application is the same. So is a virus scanner running in the background, or a search index rebuilding, or simply having eight things open at once. That is why a machine with a fast processor and a slow drive feels sluggish while an older machine with a good drive feels fine.
Take the seek time to zero and the whole machine changes character in a way that a transfer-rate figure cannot express.
This is the same argument I made in September about the Eee PC’s four gigabytes of flash, and it is worth noticing that the cheapest laptop on the market and the most expensive one have arrived at the same storage technology from opposite directions. One uses it because it is cheap at small capacities and nothing moves. The other uses it because it is fast and nothing moves. Both are right.
Two cautions before anyone spends the thousand dollars.
The controllers are uneven. The chips are commodity, but the logic that decides where writes go and how wear gets spread across the cells is not, and it varies a great deal between manufacturers. Some drives on the market right now perform beautifully when new and get erratic under sustained writing. Almost no review runs long enough to catch that.
And the cells wear out. There is a finite number of write cycles, the drive manages it, and the management is invisible until it is not.
Wait a generation or two. Then replace the drive before you replace the processor, because that is where the money buys the most.