[Yaffs] Reliability of tags in the spare area?

Hi all,

This is just a hypothetical question as I haven't encountered a real
problem, but should we be worrying about bit drop-outs in the spare area in
the same way that we do on the page data?

I've learned that some of the USB storage solutions store a small (3-4 byte)
tag and an ECC on it, as well as the ECC of the page data, in the spare
area. (Samsung, I read on a PDF I googled up, seem to use a 10 bit code over
up to 4 bytes, with the usual correct 1 / detect 2 bit error semantics.)

Is this something that we ought to consider for a later version of YAFFS?
The extra load on the spare area would appear to be unproblematic on a
large-page device: 16 bytes of packed yaffs2 tags => four 10-bit ECC blocks
=> 5 bytes of packed tags-ECC.


Ross

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