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Date:      Sun, 13 May 2007 11:44:24 +0200
From:      Erik Trulsson <>
To:        Ted Mittelstaedt <>
Cc:        Grant Peel <>,
Subject:   Re: camcontrol
Message-ID:  <>
In-Reply-To: <>
References:  <005101c7942f$ad805130$6501a8c0@GRANT> <>

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On Sun, May 13, 2007 at 01:14:57AM -0700, Ted Mittelstaedt wrote:
> > -----Original Message-----
> > From:
> > []On Behalf Of Grant Peel
> > Sent: Friday, May 11, 2007 5:51 PM
> > To:
> > Subject: Re: camcontrol
> > 
> > 
> > I have already set camcontrol to tell the system to stop using 
> > that part of the drive per the FAQ and Handbook:
> > 
> > AWRE (Auto Write Reallocation Enbld):  1
> > ARRE (Auto Read Reallocation Enbld):  1
> > But, it still tries to read the block in question (3abd5c1).
> Then you are screwed.  The drive is using some sort of remapping and
> the actual block with the problem is somewhere else.
> > It 
> > is always that same block, so the badness does not seem to be 
> > growing.Is there a way to diagnose what file it is trying to 
> > read? (perhaps I could remove that inode?)
> No and no.
> What you need to do is backup the disk, then boot into MS-DOS and
> run the disk drive manufacturer's software that forces the SCSI disk
> to update it's bad sector list and remap the bad block.
> A modern SCSI disk should NEVER show an error because it is always
> silently remapping bad sectors.

There is one situation where it is not possible to do silent remapping of
sectors.  That situation is where the bad block is discovered when trying
to read from it.  If the disk cannot read the block it does not know what
data was supposed to be there and thus cannot rewrite it to another block.

(A good RAID setup can handle that situation too, since then the controller
can find out from the other disks in the array what the data in that block
should have been.)

> All disks lose a sector now and then, that is why they have spare
> sectors and a bad sector list.  You will never see a report of a bad
> sector until the day comes that the disk has had so many sectors
> fail that it's used up it's spare sectors.
> Years ago there were some disks that while they had this capability
> it was disabled by default - I have no idea why - and when a bad sector
> did develop the disk would report it until you sent the device a
> scsi format command, then the remapping would happen.
> There are some disk programs on the Internet that can do this as
> well.

<Insert your favourite quote here.>
Erik Trulsson

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