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Re: Generalized Flash question



>> Somebody told me a week ago that flash only works well if you
>> write to it very infrequently because it, well breaks.

> It breaks after X erase-cycles, where X is usually a very large
> number today (I don't have any datasheets here, but I'd
> guess X > 100,000).

X is between 1,000 and 1,000,000 - often 10,000 based on a
failure rate of less than 1%.

> JFFS does rudimentary wear-levelling because of the log-structured
> design, we write new data at the end of the circular log instead of
> rewriting the block where the old data was. More advanced algorithms
> will come eventually..

I don't know much about JFFS. Is there a kind of allocation table in a
fixed block comparable to FAT based file systems? There were many
discussions about the flash in the Beck IPC@chip (a chip with processor,
ethernet, RAM and flash integrated). As far as I understood, the result
was that the OS of the IPC@Chip uses allocation table in a fixed block
which is updated twice during a write operation on any file. So the
allocation table will break after writing about 5,000 files, even if they
are
at different locations.

How does the JFFS handle this?

Thomas





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