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SubjectRe: New filesystem for Linux
>>> And possibly some broken drives may also return you something that
>>> they think is good data but really is not (shouldn't happen since
>>> both disks and cables should be protected by checksums, but hey...
>>> you can never be absolutely sure especially on very big storages).
>
> It happens because
> - There is limited if any protection on the PCI bus generally
> - Many PC systems don't have ECC memory, ECC cache
> - PATA does not CRC protect the command block so if you do enough PATA
> I/O (eg you are a US national lab ..) you *will* eventually get a bit
> flip that gives you the wrong sector with no error data. SATA fixes that
> one.
> - Murphy is out to get you..

Should IDE driver read back parameters after writing them before issuing
the command? That should fix this problem. (except when command is written
badly)

> Not seen that, although they do move stuff aorund in their internal
> block management of bad blocks. I've also seen hardware errors that lead
> to data being messed up silently.

I have seen one WD drive bought in 2003 having error in its firmware in
cache-coherency code --- if you read and write 256 sectors to the same
places with some pattern repeatedly (with direct IO), it will discard a
write. It happens only with 256-sector writes, maybe some part of firmware
treats 256 as 0. Maybe I create testcase sometimes.

Mikulas

> Alan
>
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