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Re: Bad Blocks in IDE software Raid 1

Hello Russell 

On 15 Apr 2003 at 20:21, Russell Coker wrote:

> If you do a write and something goes wrong then the data will be re-mapped.  I 
> don't know how many (if any) drives do "read after write" verification.  If 
> they don't then it's likely that an error will only be discovered some time 
> later when you want to read the data (and this can happen even if the data is 
> verified).
> Then the drive will return a read error.  If you then write to the bad block 
> the drive will usually perform a re-mapping and after that things will be 
> fine.
> If using software RAID then a raidhotadd operation will usually trigger a 
> re-mapping on the sector that caused the disk in question to be removed from 
> the array.

Am I correct in assuming that every time a "bad block" is discovered 
and remapped on a software raid1 system:

- there is some data loss

- one of the drives is failed out of the array

I assume there are repeated attempts at reading the bad block, before 
the above actions are triggerd. Hopefully these will trigger remapping 
at the firmware level before the above happens.

Do you think there would be any benefit gained from "burning in" a 
new drive, perhaps by running "fsck -c -c", in order to find marginal 
blocks and get them mapped out before the drive is put onto an array?

What about doing this on a aray drive that has "failed" before 
attempting to remount it with "raidhotadd".


Ian Forbes ZSD
Office: +27 21 683-1388  Fax: +27 21 674-1106
Snail Mail: P.O. Box 46827, Glosderry, 7702, South Africa

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