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    SubjectRe: Why are bad disk sectors numbered strangely, and what happens to them?
    Rogier Wolff wrote:

    >On Tue, Oct 14, 2003 at 12:45:34PM +0400, Hans Reiser wrote:
    >
    >
    >>Perhaps we should tell people to first write to the bad block, and only
    >>if the block remains bad after triggering the remapping by writing to it
    >>should you make any effort to get the filesystem to remap it for you.
    >>What do you think?
    >>
    >>Rogier has not indicated that he has tried writing to the bad sector,
    >>has he?
    >>
    >>
    >
    >Hans,
    >
    >I simply refuse to try to trigger a remapping by writing to the
    >sector. A couple of things can happen:
    >
    >1) The write succeeds on the "bad" spot.
    >
    > The "normal" write doesn't
    >do a "veriy-after-write", so the write might simply be succeeding,
    >resulting in an immediate data-loss (which might be masked if I try
    >to reread the data from userspace bacause the data is still cached!)
    >
    Do a hard reboot with > 25 seconds power off.

    >
    >2) the realloc might succeed, hiding the fact that my drive just lost
    >0.5k bytes of my data. I mean, there was SOME data there. Linux
    >wouldn't try to be reading it if it had never been written, right? A
    >drive that refers my data to /dev/null should be diverted there
    >itself.
    >
    >Of course, I left my drive that indicated it had problems (i.e. it
    >didn't spot the sector going bad before it became unreadable), in the
    >machine for another two days. It's getting replaced ASAP (i.e. the
    >next hour or so).
    >
    >The bad sector developed in a backup of data that is still running
    >hapilly on another machine. But I'm not risking a sector getting
    >assigned some important data going bad next time I notice something.
    >
    > Roger.
    >
    >
    >
    replacing the drive is reasonable caution. I think though that the
    other poster is right that IFF you want to remap bad blocks, the drive
    should do it not reiserfs.

    --
    Hans


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