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SubjectRe: software RAID
Yes, I want to know if the bad sector on disk A will be reallocated
when disk B tries to write to disk A.


On Fri, 20 May 2005, Grzegorz Kulewski wrote:

> On Fri, 20 May 2005, Lennart Sorensen wrote:
>> On Fri, May 20, 2005 at 12:56:13PM -0500, Adam Miller wrote:
>>> We're looking to set up either software RAID 1 or RAID 10 using 2 SATA
>>> disks. If a disk in drive A has a bad sector, can it be setup so that the
>>> array will read the sector from drive B and then have it rewrite the
>>> bad sector on drive A? Please CC me in the response.
>> If a harddisk has a bad sector that is visible to the user (and hence
>> not remapped by the drive) then it is time to retire the drive since it
>> is out of spares and very damaged by that point.
>> If you have a bad sector, it doesn't go away by writing to it again. On
>> modern drives, if you see bad sectors the disk is just about dead, and
>> will probably be seen as such by the raid system which will then stop
>> using the disk entirely and expect you to replace it ASAP.
> What do you mean "see bad sectors"?
> Modern drives are trying to relocate sectors that can become bad in short
> time. But this does not work 100% reliably. And sometimes disk wants to
> relocate sector but the sector can not be read anymore. If this happens disk
> will return read error when reading the sector _but_ when you will write it
> again it will relocate it (with new data). And I think this was the idea
> behind first post... To allow disk A to relocate not readable sectors with
> correct data from disk B.
> Grzegorz Kulewski
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