[maemo-users] Limited life of flash memory

From: Frantisek Dufka dufkaf at seznam.cz
Date: Wed Dec 3 11:01:28 EET 2008
Mark wrote:
> On Tue, Dec 2, 2008 at 9:36 AM, Igor Stoppa <igor.stoppa at nokia.com> wrote:
>> I can only repeat my advice: why don't you do some reading at least
>> about jffs2?
> Because it's irrelevant in discussions about removable flash memory.

How do you know if you did not read it? :-) I wouldn't be surprised if 
jffs2 technical documentation would discuss NAND pecularities and wear 
levelling details.

Also http://en.wikipedia.org/wiki/Wear_leveling and pdf whitepapers 
linked on the bottom could explain a lot.

> Another issue is that wear levelling depends on there being a certain
> amount of free memory in order to shuffle the data around. Most use
> dynamic rather than static wear levelling, which reduces the
> effectiveness even further when there is little free space.

Flash translation layer in memory cards does not know about 'free 
space', that is filesystem related thing one layer above, we are talking 
about pure data blocks with no meaning here.

That is actually one thing to improve in future, filesystem should let 
the flash device driver know which blocks are free so it can be more 
creative with them.


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