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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?
>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
>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.


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