bad sector in gmirror HDD

[Dan Langille]

On Aug 19, 2011, at 7:21 PM, Jeremy Chadwick wrote:

> On Fri, Aug 19, 2011 at 04:50:01PM -0400, Dan Langille wrote:
>> System in question: FreeBSD 8.2-STABLE #3: Thu Mar  3 04:52:04 GMT 2011
>> 
>> After a recent power failure, I'm seeing this in my logs:
>> 
>> Aug 19 20:36:34 bast smartd[1575]: Device: /dev/ad2, 2 Currently unreadable (pending) sectors
> 
> I doubt this is related to a power failure.
> 
>> Searching on that error message, I was led to believe that identifying the bad sector and
>> running dd to read it would cause the HDD to reallocate that bad block.
>> 
>>  http://smartmontools.sourceforge.net/badblockhowto.html
> 
> This is incorrect (meaning you've misunderstood what's written there).
> 
> Unreadable LBAs can be a result of the LBA being actually bad (as in
> uncorrectable), or the LBA being marked "suspect".  In either case the
> LBA will return an I/O error when read.
> 
> If the LBAs are marked "suspect", the drive will perform re-analysis of
> the LBA (to determine if the LBA can be read and the data re-mapped, or
> if it cannot then the LBA is marked uncorrectable) when you **write** to
> the LBA.
> 
> The above smartd output doesn't tell me much.  Providing actual SMART
> attribute data (smartctl -a) for the drive would help.  The brand of the
> drive, the firmware version, and the model all matter -- every drive
> behaves a little differently.

Information such as this?  http://beta.freebsddiary.org/smart-fixing-bad-sector.php


-- 
Dan Langille - http://langille.org