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Harddisk Density vs Data Retention Time ???



 
 
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  #1  
Old February 24th 21, 02:57 AM posted to alt.comp.hardware.pc-homebuilt
skybuck2000
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Posts: 61
Default Harddisk Density vs Data Retention Time ???

Question:

Does the Data Retention Time of a magnetic harddisk decrease as it's magnetic density increases ?!?

My hypothesis would be: the higher the density, the smaller the magnets, the weaker the magnetic field thus faster data loss ?!?

Thoughts ?

Bye,
Skybuck.
  #2  
Old February 24th 21, 03:48 AM posted to alt.comp.hardware.pc-homebuilt
Paul[_28_]
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Posts: 1,467
Default Harddisk Density vs Data Retention Time ???

skybuck2000 wrote:
Question:

Does the Data Retention Time of a magnetic harddisk decrease as it's magnetic density increases ?!?

My hypothesis would be: the higher the density, the smaller the magnets, the weaker the magnetic field thus faster data loss ?!?

Thoughts ?

Bye,
Skybuck.


Data storage is three-dimensional, not two-dimensional.

This is why vertical recording is every bit as good
as longitudinal recording (the original method).

Vertical recording uses a "backing plate" which is
buried below the surface plating. This completes
the magnetic circuit and the plate functions as
a "holder", amongst other things. Longitudinal
recording did not need this, because the flux
pointed in a different direction.

The platters can be made from non-ferrous materials.
The platters could be aluminum or glass. With glass
currently being preferred for, say, 18TB drives with
nine platters. The glass can be made thinner, which
allows the head stack to contain more platters for
the ~1" height of the drive. Then, a complicated series
of plated-up layers, established the environment the
recorded bits will live in. For the digital bits, the
platter material is irrelevant to their operation.

If the manufacturers are honest about their work, they
place some information in the web pages, indicating
that some properties were harder to meet than others.
For example, perpendicular recording drives might have
been slightly more susceptible to externally applied
magnetic fields. But the manufacturer claimed they
"changed something in the design, to make the new drives
resist external magnets, just as well as previous drives".

They do attempt to get equal performance from the drives.

Except when they outright lie, such as SMR and "how wonderful
they are". Third parties have to rub their noses in it, before
they will admit they should have been more honest about how
poor SMR drives are. And sticking SMR in low-end drives,
was just as shabby a business plan, as we would expect
from businesses. Even when there was not particularly
a need to do it. They were doing stuff like that because
"our shareholders appreciate it, when we make crap". In
some cases, at the density point in question, there was
little to be gained by doing it, except as a mechanism to
collect field failure data for future designs. That's about
the only excuse I can find. For example, one drive was able
to remove one platter, whereas the previous drive was "almost
perfect for consumers", since it held up well and did not
seem to be crap. (The platters might well have been cheaper
to make, as they were not density limited.) A poster in the
WinXP group was buying those, for as long as he could get them.

Paul
  #3  
Old February 24th 21, 10:54 AM posted to alt.comp.hardware.pc-homebuilt
Flasherly[_2_]
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Posts: 2,407
Default Harddisk Density vs Data Retention Time ???

On Tue, 23 Feb 2021 17:57:20 -0800 (PST), skybuck2000
wrote:

Question:

Does the Data Retention Time of a magnetic harddisk decrease as it's magnetic density increases ?!?

My hypothesis would be: the higher the density, the smaller the magnets, the weaker the magnetic field thus faster data loss ?!?

Thoughts ?

Bye,
Skybuck.


Flux and permeability.

http://hyperphysics.gsu.edu/hbase/Solids/ferro.html#c3
 




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