Re: Support of removable MTD devices and other advanced features (follow-up from lkml)

Jörn Engel
2008-05-25T16:24:40Z

On Sun, 25 May 2008 14:30:29 +0100, Jamie Lokier wrote:
> Jörn Engel wrote:
> > > Memorystick cards can be written page at a time, but only in progressive
> > > fashion - only if all pages at lower offsets to the current page were written
> > > before. This can be made to work as a useful optimization.
> >
> > The same limitation is true for some raw NAND chips as well. Afaik all
> > of current MTD honors that limitation.
>
> That seems like it would cause uneven wear-levelling in some
> situations. Specifically, each time you need to erase a block which
> has not been completely written, because you need to write a
> contiguous record larger than the remaining space.
>
> I don't know it was a physical requirement of some chips, thanks for
> clarifying.

The "progressive" limitation only concerns writes _within_ eraseblocks.
It has no impact on wear leveling.

Jörn

--
If you're willing to restrict the flexibility of your approach,
you can almost always do something better.
-- John Carmack