[ltp] Re: T420s HD life and Load Cycle counter

[Henrique de Moraes Holschuh]

On Sun, 03 Jul 2011, Stefan Monnier wrote:
> > I just had a look at SMART results for my two months old T420s running
> > the tlp daemon and I noticed that the number of Load Cycles for the HD
> > has already reached 117000, with a "power on" of 887 hours.
> 
> Laoptop (and low power desktop drives) are designed to do such "load
> cycle" *very* often.  This number is unrelated to the number of

100k to 300k cycles over the entire drive lifetime on the lesser devices,
600k on the good stuff like Hitachi HDDs.  You can kill a heavy drive in a
couple years if it unloads heads too often (once every few seconds) and your
system is not heavily optimized to avoid background HDD access.

This is listed in the complete drive datasheet.

> spin-up/spin-down; and other than FUD, there's no evidence that high
> numbers are a sign of problems to come.  Many manufacturers have simply

Head unloading slowly degrades the head support integrity, due to flex.  You
can actually hear when the drive does it, btw: a very soft "click".

Spin up/down is also a problem, and eventually might also kill the device.
HOWEVER the fluid bearings in some HDDs might actually _REQUIRE_ spin
up/down cycles every so often to not degrade, it is the case of the 7K100 in
my T43 (and this _is_ stated clearly in the datasheet: required to spin down
at least once every 48H).

> removed this Load_cycle_count from the smart output since its effect
> seemed to be limited to instilling fear in some of their customers.

Which ones, so that I can avoid them like the plague?

Unloading heads is important for two reasons: unloaded heads are far less
succeptible to damage due to sudden impacts to the drive, and allow for the
linear head assembly positioning motor to be either turned off, or operated
in reduced current.

So, it reduces idle power consumption of the drive, which is of paramount
importance for the vendor's marketing department since everyone overstates
their battery longevity numbers.  It can also decrease the chance of a
damaged drive that needs to be returned in warrany on the cheap-o crap 1yr
warranty service.

Removing Load Cycle Count is just unethical.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh