Re: 'let the hdd remap the bad blocks'

[Hans Reiser <reiser@namesys.com>]

Oleg Drokin wrote:

>Hello!
>
>   Basically uyou'd better search for this on HDD vendors sites.
>   What's going on is simply can be described this way:
>   You write some block to HDD, if HDD decides the block is bad for some reason
>   and remapping is allowed (usually by tiurning on SMART), block is written to
>   different on-platter location and drive adds one more entry to its
>   remaped-blocks list. Next time you read this block, drive consults its
>   remapped blocks list and if block is remapped, reads it from new location
>   with correct content.
>   Described mechanism works for writing.
>   Actually I've seen something that looks like remapping on read, though 
>   I have no meaningful explanation for that (except that they may have some
>   extra redundant info stored when you write data to disk, so that if sector
>   cannot be read, its content is restored with that redundant information and
>   sector is then remapped.). And this process takes a lot of time.
>
>Bye,
>    Oleg
>On Mon, Aug 19, 2002 at 03:58:30PM +0100, Newsmail wrote:
>  
>
>>Hello Hans and Oleg,
>>maybe its an offtopic question, but Hans always talks about leaving the 
>>hard disk to remap the bad blocks by itself. could you explain it in some 
>>words, how all this works, what happens after, and since when it exists, or 
>>do you have any special URL explaining this?
>>thx in advance,
>>greg
>>
>>
>>
>>    
>>
>
>
>  
>
Just taking a guess, many hard drives have difficult and time-consuming 
procedures that they can go through to read a troublesome block.  These 
can take 20-30 seconds.  Probably if they have to go through these 
procedures, once they finally succeed the smart vendors remap the block.

Hans