Windows Vista feature: ReadyBoost

I was reading Chris Pirillo’s blog today and found a post about a feature in Windows Vista: ReadyBoost. I went to Microsoft’s web site and found a page listing the feature within the performance features of Vista:

Windows Vista introduces a new concept in adding memory to a system. Windows ReadyBoost lets users use a removable flash memory device, such as a USB thumb drive, to improve system performance without opening the box. Windows ReadyBoost can improve system performance because it can retrieve data kept on the flash memory more quickly than it can retrieve data kept on the hard disk, decreasing the time you need to wait for your PC to respond.

Now, I don’t claim to be up on the technical details of flash memory. However, I was always under the understanding there was a limited number of times flash memory could be overwritten. I was reading in a computer magazine around 10 years ago about how you could only flash your BIOS 10,000 times because it was a flash memory limitation (OK…I know, “only” isn’t a word you tend to asssociate with the number 10,000). About 3 years ago, Microsoft sent me 4 32MB flash drives for attending one of their Windows Server 2003 Partner Readiness events. The packaging said it could be re-written approximately 100,000 times.

Every once in a while, I read articles talking about replacing hard drives in laptops with flash drives. I’m sitting here wondering about the practicality of this. Think about how often the swap file must be written to. I’ve been on support calls where they’ve had me use regtrace. It’s amazing, the number of times the registry is written to during normal computer operation. Now, Microsoft has ReadyBoost. Again, I must wonder at the practicality. The flash drive will basically be an extension or RAM — just like the page file.

Last week, during my musings on flash drives replacing hard drives in laptops, I decided to search for limitations on the number of times flash drives can have their memory rewritten. My searching lead me to an article at AskLeo! that addressed my concern:

The “problem” is that memory can be flashed only so many times. I’m finding numbers between 10,000 and 100,000 times – though as with anything, I’m sure that is increasing over time as well. Regardless, there is a limit. When that limit is approached, some portion of the memory may not properly remember what was written to it, resulting in corruption. It may only take a single bit of information to be wrong, or to “wear out”, for the entire contents of a flash memory chip to be lost.

Hmm. However, that’s followed up by this:

Some flash memory chips, perhaps even most, now also include circuitry to avoid “bad bits”. Meaning that if portion of the flash memory finally wears out and goes bad, the chip itself can compensate and look like everything is fine. But that only lasts so long … it doesn’t prevent failure, it only postpones it.

So there you go. Sure, 100,000 is a lot of times. For regular file archiving or transport, you’re extremely unlikely to re-write any of the flash cells on a flash drive 100,000 times before you’d be looking into upgrading to a higher capacity. However, the number of times RAM and a swap file get written to can add up very quickly. I’m interested to see how this ends up playing out.