[Yaffs] bit error rates --> a vendor speaks

Thomas Gleixner tglx at linutronix.de
Sat Feb 18 04:10:25 EST 2006


On Thu, 2006-02-16 at 14:32 +1300, Charles Manning wrote:
> 1) ECC on tags....  Tags are so small that a single-bit correction is probably 
> enough. Multibit is probably a good thing to investigate.
> 2) More OOB being used for multi-bit schemes will probably mean less space 
> available for tags.

We really should start to think seriously about oob usage for arbitrary
data storage at all. I know that YAFFS(2) depends on that, but looking
at the required mess in the code to keep this up for all the 9999
variants of ECC/RS whatever mechanisms, bad block marking schemes ...

Some words about Reed Solomon.

Reed Solomon needs hardware support for performance reasons. Efficient
usage of Reed Solomon requires a different Data / RS-code layout:

512 Byte Data
8 Byte RS Code
512 Byte Data
8 Byte RS Code
512 Byte Data
8 Byte RS Code
512 Byte Data
8 Byte RS Code
32 Byte OOB

This layout is supported already (see rtc_from4.c). It requires usage of
flash based bad block tables.


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