On 7/6/2010 10:27 AM, Mike Lazzari wrote:
> If fewer platters means less risk of failure ...
If you are referring to what I said, that's not what I said, or at least meant
to say. What I meant to say is that the
change from 4 to 5 platters in the same form factor may result in short term
higher risks of failure, as a result of the
mechanical changes.
Simple example: To squeeze more into less space would likely mean a shorter
spindle bearing, at the same time as the
rotating mass increases. So engineers design and test a new bearing. That's
trickier than it may seem. In a ideal
theoretical case, there are no wobble motions. In the real world, the bearing
must handle wobble. A big factor then is
the lever arm and mass of the spindle vs. the length of the bearing. Shorter
bearing means larger loads, heavier
spindle/platter assembly means greater loads. So the new design has to handle
greater loads in a smaller part, within
cost and manufacturing constraints.
Probably, it works in the real world, but maybe too many of them fail. Redesign
again, succeed, and all is well going
forward.
Multiply that by many redesigned parts, and the chance for an initial failure
rate higher than the established previous
design becomes significant. After the new standard settles down, I'd expect
failure rates to settle down to about what
they were before.
Moose
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