Re: [Yaffs] How does YAFFS handle Memory deterioration?

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Author: Charles Manning
Date:  
To: yaffs
CC: Jimmie Hansson
Old-Topics: [Yaffs] How does YAFFS handle Memory deterioration?
Subject: Re: [Yaffs] How does YAFFS handle Memory deterioration?
On Monday 03 June 2013 06:07:59 Jimmie Hansson wrote:
> Hi
>
> I am considering using YAFFS for storing pictures on a NAND flash in a
> device that need to be able to function for 30 years. The pictures on the
> NAND flash will get written to the flash when it gets manufactured and then
> the device will rewrite the pictures every year so that the pictures don’t
> get corrupt from memory deterioration. The data retention on a normal NAND
> flash is about 10 years.
>
> Is YAFFS a file system that will be suitable for this kind of long life
> application?
>
> How does YAFFS handle Memory deterioration?
>
> Will it be enough for me to rewrite a file every year for it to not get
> corrupt of memory deterioration or are there any other crucial data in the
> file system that will get corrupt over time?


Hello Jimmie

I think that would work pretty well.

If you are going to make a product like that then I would be careful to test
any implications of http://en.wikipedia.org/wiki/Year_2038_problem

Yaffs does not really have other data to get corrupted. There is no FAT table
or such. That actually makes it a very good candidate for the type of usage
you are considering.

There is a very small chance that old stuff in the log (ie. discarded data)
could come alive again through "bit rot". It would make some sense to do some
background garbage collection to clear this up. This is already wired into
Linux but can easily be hooked up with other OSs.


-- CHarles