Re: Are linux-fs's drive-fault-tolerant by concept?

[Helge Hafting <helgehaf@aitel.hist.no>]

On Sat, Apr 19, 2003 at 05:15:31PM -0400, Valdis.Kletnieks@vt.edu wrote:
> On Sat, 19 Apr 2003 22:56:21 +0200, Helge Hafting said:
> 
> > There are commercially available programs that guarantees to
> > wipe your drive clean - including hidden areas and remapped
> > sectors.  You should then be able to send drives
> > back for warranty replacement.
> 
> These don't address the problem - if the drive won't go "ready" because
> of a blown server platter, your data won't get overwritten but it's still
> readable (a number of companies make good money at this).
> 
I see.  Your data is so special that you expect people to pay for
reconstruction hoping to find something that pays for all
that trouble and more.

> In general, if the disk is dead enough that you're looking at replacement,
> you'll probably not be totally pleased with the results of those programs..
> 
I have replaced a couple of drives in my life - because a few sectors
didn't read back right.  I expect a overwrite program to be just
fine under such circumstances.  

> > There are also bulk erasers that reset every bit magnetically,
> > but those will probably void the warranty too.  (You'll
> > need a low-level reformat to recreate sector addresses on the
> > suddenly blank surface.)
> 
> Note that this only works well for single-platter disks - the field
> you need to get the *inner* surfaces of the platters, especially for
> a 5 or 6 platter disk, is quite astounding....

Why would it be hard to reach the inner surfaces - the disks
are not superconducting so the outer ones do not shield the
inner ones from a strong magnetic field.  You should be fine
as long as the field extend far enough to get the entire
drive.  A high-frequency device might have trouble,
but you don't need that - even a static field will do.

Helge Hafting