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Re: SSDs have extra "unused" space??? (was: Re: Bug#735927: general: X *always* crashes when ram is full

On Tue, Jan 21, 2014 at 1:22 AM, Holger Levsen wrote:

> wait, what? Do you have any vendor statements to support this 20% extra space?

Flash is basically probabilistic storage and you need extra space to
ensure that the probability your data is stored remains high, and a
(possibly trustworthy) controller with algorithms in front to help
with that. Check out Bunnie's talk at 30C3 about SD cards where he
mentioned a 16GB flash device with the controller only saying it was
128MB in size (IIRC). I assume similar things apply to SSDs/NAND etc.




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