Re: Why are bad disk sectors numbered strangely, and what happensto them?

[Hans Reiser]

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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