Re: Driver retries disk errors.

[Rogier Wolff]

On Mon, Aug 30, 2004 at 06:17:24PM -0600, Robert Hancock wrote:
> Quite likely, in that case the drive has exhausted its spare pool, and 
> there are a bunch of bad sectors that have already been reallocated. Some 
> drives will reallocate sectors if they are still readable but the sector 
> appears to be marginal.

I agree that this is the theory. In practise however, I've never
seen it work correctly. We've seen several disks with say 1-5 bad
blocks and nothing else, and "dd if=/dev/zero of=/dev/<disk>" doesn't
seem to cure them.

I know how to check SMART, and I can see that some of these disks
have NEVER reallocated a block. Stuff like that. 

	Roger. 


> ----- Original Message ----- 
> From: "Rogier Wolff" <R.E.Wolff@xxxxxxxxxxxxxxxxxxxx>
> Newsgroups: fa.linux.kernel
> To: "Theodore Ts'o" <tytso@xxxxxxx>; <linux-kernel@xxxxxxxxxxxxxxx>; 
> <linux-ide@xxxxxxxxxxxxxxx>
> Sent: Monday, August 30, 2004 4:19 PM
> Subject: Re: Driver retries disk errors.
> 
> 
> >On Mon, Aug 30, 2004 at 01:46:32PM -0400, Theodore Ts'o wrote:
> >>> a filesystem: if we recover one block this way, the next block will be
> >>> errorred and the filesystem "crashes" anyway. In fact this behaviour
> >>> may masquerade the first warnings that something is going wrong....
> >>
> >>If the block gets successfully read after 2 or 3 tries, it might be a
> >>good idea for the kernel to automatically do a forced rewrite of the
> >>block, which should cause the disk to do its own disk block
> >>sparing/reassignment.
> >
> >Hi Ted,
> >
> >I agree that this is the theory. In practise however, I've never
> >seen it work correctly. We've seen several disks with say 1-5 bad
> >blocks and nothing else, and "dd if=/dev/zero of=/dev/<disk>" doesn't
> >seem to cure them.
> >
> >Roger.
> >
> >-- 
> >+-- Rogier Wolff -- www.harddisk-recovery.nl -- 0800 220 20 20 --
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