HDD

[Poul-Henning Kamp]

In message <0D162CCAE42F819501B87257 at cc-126-240.int.t-online.fr>, Mathieu Arnol
d writes:
>+-le 14/12/2005 17:45 +0100, Alexandre DELAY =E9crivait :
>| Don't you think that flash drives are also a good solution?
>|=20
>| I am sure that it will be the future replacement for hard drive disks.
>| see http://www.memtech.com/ for example
>|=20
>| With no buffer and 1ms access delay you minimise write failures. It is an
>| interresting solution.
>
>Hum, flash has a *limited* ammount of possible write for each cell, for low
>cost, it's between 10K-50K and for heavy duty, industrial grade, bla bla bla,
>it's around 2M, so, hum, just imagine you have a solid state flash disk, and
>your swap on it. One day, your box begins swapping hard, and some time later,
>half of your drive can't be written to again...

Sorry but that is not how flash devices work.

There is a very important piece of technology called a "flash
adaptation layer" which performs what is usually called "wear
levelling" in an attempt to get the maximum amount of lifetime out
of the entire device by using a dynamic logical to physical mapping
and keeping track of bad cells etc etc.

Yes, you will kill a flash by doing a lot of writes, but it will
not develop individual bad sectors like a disk.

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