Life of a byte on the hard disk

Franc Zabkar wrote in news:3s8e34ptv5bjjie5o8u4356gu876jojiq7@4ax.com
> On Wed, 21 May 2008 19:26:28 +0800, "Man-wai Chang ToDie (33.6k)"
> <toylet.toylet@gmail.com> put finger to keyboard and composed:
>
> >
> > The hard disk stores a byte by some kind of magnetism.
> >
> > If I don't touch that byte on the disk for a long time, would it
> > lose magnetism and hence that byte of information?
> >
> > After how long would that happen?
>
> Refreshing your data may get around that problem, if it is a real one,
> but there would be no way for the user to refresh the embedded servo
> information that was prerecorded at the factory.

Let me quess, you came up with that all by yourself, right?

>
> Here is John Navas's response to claims by Steve Gibson, the author of
> Spinrite, that "magnetic patterns 'weaken' over time":
> http://groups.google.com/group/comp....eee32323c2978e

Navas is a just as opiniated as Gibson, lots of rhetoric.
Do patterns weaken? Yes and No. Read sensivity of the heads may worsen
over time, wear and tear (contamination) may have its effects on fly height
and writes may not be as strong as earlier in life, the overall effect is the
same: what may have been readable first may well not be later.

Is writing back data a refreshing of data? No, but rewriting a
weak sector to a different area may well be accepted as such.
It is not about the 'fresh'ness, it's about the (presumably) better
quality of the area where the data is 're'stored.

Oh, and what may be a cure in one incident can be a plague in another,
if the drive develops a fault in the write element:
once perfectly readable sectors may be unreadable after a rewrite (refresh).

>
> - Franc Zabkar