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

[Hans Reiser <reiser@namesys.com>]

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