Messages in this thread | | | Date | Sun, 5 Nov 2006 18:18:07 +0100 (CET) | From | Mikulas Patocka <> | Subject | Re: New filesystem for Linux |
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>>> 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
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