Andreas --

Thank you for your response; what I ended up doing was failing the disk (it was in a raid 1 configuration and the error was showing up everytime the mdadm checked the array); ran badblock in destructive mode (write checks) which found no badblocks; rechecked the array with smartctl (it turned up clean) and then readded it to the array; after a long rebuild build (less than a day) all was clean :)
-
Naturally if this had been a non-raided disk I would have need to do something alternative.

--- On Mon, 9/10/12, Andreas Mohr <andim2@users.sourceforge.net> wrote:

From: Andreas Mohr <andim2@users.sourceforge.net>
Subject: Re: [smartmontools-support] how to clear bad block if block is readable ?
To: smartmontools-support@lists.sourceforge.net
Cc: "a a" <you2bepie@yahoo.com>
Date: Monday, September 10, 2012, 3:10 AM

Hi,

On Mon, Sep 10, 2012 at 06:17:10AM +0000, smartmontools-support-request@lists.sourceforge.net wrote:
> The first bad block 26587969 the dd trick worked fine:
> /dev/sdb1????????????? 63? 1758667679?? 879333808+? fd? Linux raid autodetect
> dd if=/dev/zero of=/dev/sdb1 bs=4096 count=1 seek=3323488
> --
> However I am unable to clear the second bad block (dd does not hang with a sense error and the write does not remap it). This disk is used in a linux software raid 1 configuration.
> -
> The question is how to do I clear this error so smartctl can continue the scan ?
> (I'm 100% sure this block is not covering important data )
> ?

Ouch, sounds fun, a bad sector which does not get sufficiently recognized as "bad"
to initiate remapping yet causes SMART scans to freak out.

I think tutorials about advanced uses of *GNU* ddrescue (gddrescue)
(e.g. docs talking about ddrescue fill mode etc.) may cover this item, too.

Or possibly the very nice sg3-tools toolset has some lowlevel help for this
which is usable by ATA-based disks, too (but of course be careful
with certain parts of these tools!).

HTH,

Andreas Mohr