Questions about NAND (double)bit errors

[Jamie Lokier]

Charles Manning wrote:
> > About bad block detection: what is your oppinion about partitioning the
> > flash (the programs in a read-only partition, the data in r/w).
> 
> This gets fs specific. With YAFFS (and I assume JFFS2, but consult
> an expert), grabage collection will force read-only files to get
> rewritten occasionally.  Thus for ultimate reliability it is
> probably a GoodIdea to seperate the read-only stuff into a seperate
> partition. This is also a GoodIdea in that a smaller partition
> mounts faster (true for YAFFS and JFFS2). So if all your kernel +
> mount stuff is seperated from your rw stuff things will probably dgo
> better.

Absolutely.

I've been testing 40 devices lately, and in 2 weeks, 5 of them (out of 40)
have corrupted files in JFFS2 when those files aren't being written.
I haven't seen any errors in the ROMFS partitions.

I'm still getting round to analysing the corrupt files / filesystems,
because that failure rate is too high even for configuration files
that are written from time to time.

These are 8MB chips, so presumably NOR.

-- Jamie