[Bug 59695] Re: High frequency of load/unload cycles on some hard disks may shorten lifetime

[Isaac Dupree]

Steve Langasek: sure, there's a tradeoff... but with sufficient
knowledge, perhaps we could make it less bad.  Suppose the hard-drive is
specced to 600000 load-cycles.  With smartctl we can measure the current
number of load-cycles.  Suppose there have already been 700000 load-
cycles: wouldn't you think it'd be pushing your luck to park the head
frequently, even if it saves power in the short run?  More seriously,
suppose you decrease or stop that behavior earlier, say at 500000 or
300000 load-cycles: so an older drive will use more power on battery,
but at least Linux would then obey the principle of "do no harm".  (If
the hard-drive dies, the user has to replace it; if the hard-drive is
just inefficient, the user still has the choice of replacing it, and is
also less likely to lose data.)

Now we can look at something desired like "There should be fewer than
~15 load cycles per hour, except during heavy usage while on battery."
that makes new drives last at least four years... if we adjust that
number "15" in proportion to the actual (spec - load_cycle_count), then
we'll manage to keep the drive pretty much safe from this kind of
wearing-out!

however!

- we may not know the spec (is it bad to assume that it's 600000)?

- hard drives seem to be quite uncooperative: there might not be *any*
good way to tell one "don't park any more often than X times an hour",
even though there's a darned simple algorithm (disk remembers the last
time it parked the head, and refuses to park the head again for the next
1/X hours).  But maybe there's a way we can ensure that (frequent hdparm
-B to different values? Is doing that likely to wear out the drive in
any odd way?)

-- 
High frequency of load/unload cycles on some hard disks may shorten lifetime
https://bugs.launchpad.net/bugs/59695
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