[svlug] Files That Will Not Delete

Scottix scottix at gmail.com
Wed Nov 5 00:11:01 PST 2014


Hey Greg,
Nothing you said contradicted what was said. Yes the desktop/laptop
HDD will try hard to recover a bad sector when it encounters it
(encounter is key). Yes it will remap the sector in the reserved
spaces, which can slow access to those regions. Which can cause
timeout issues with other operations. In those scenarios you can have
problems but no data is actually lost or damaged.
The other type where a sector is bad and the data doesn't exist
anywhere else, could be an issue. Recovery of that data could be
possible with a program that never gives up and tries many different
ways to recover that data.
Maybe you confused me with the second is it tries to read the sector
(which could be a problem) and puts it into memory then writes it back
to disk and yes if that sector is bad it will remap it on the write
not the read generally, but you have to recover the data first
otherwise what is the point.

Yes RAID is a different beast and has other ways to deal with
failures, although my laptop did not come with a RAID system so I am
out of luck there.

On Tue, Nov 4, 2014 at 9:50 PM, Greg Lindahl <lindahl at pbm.com> wrote:
> On Tue, Nov 04, 2014 at 04:42:18PM -0800, Scottix wrote:
>
>> First is it tries to read every sector on the drive, through various
>> methods and won't give up after a long time
>> Second is a read and then write sectors back to disk.
>
> Uh, that's stupid. Modern systems retry reads a crapload of times
> before they give up. Given that the data is lost, the way to clear the
> problem is to write *without* reading. But what do I know, I only have
> 8,000 drives?  Fortunately, my friends have a lot more, and they agree
> with me.
>
> RAID systems with redundancy write without reading once they realize
> the data is lost. That tells the drive that it can give up on what is
> lost, and stick in a reallocated sector. 20%, remember?
>
> No snake oil needed.
>
> -- greg
>
>
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