Archived from groups: comp.sys.ibm.pc.hardware.storage (
More info?)
DanR wrote:
>
>
> J. Clarke wrote:
>> Jack Tyler wrote:
>>
>>> I have seen various comments like "we leave our servers running 24/7
>>> because powering up a hard drive causes more wear than leaving it
>>> running."
>>
>> This is the conventional wisdom. And it's not just disks. Thermal
>> cycling used to be a serious problem with computers--that's why memory
>> sockets have
>> latches now. On an original IBM PC that had been running for a couple of
>> years, sometimes the memory chips would walk completely out of the socket
>> due to repeated thermal cycling.
>>
>>> I think it's mostly laziness and apathy about conserving
>>> energy.
>>
>> Shutting down a large server farm is not something to be done lightly.
>> Bringing it down and back up in an orderly fashion might take more than
>> one night.
>>
>>> The TiVo forums discuss it a lot because a standard TiVo HD
>>> runs all the time, buffering 30 minutes of whatever channel it's left
>>> on.
>>
>> Yep, and they seem to last and last.
>>
>>> Do IT people who leave servers running 24/7 ever have much choice of
>>> NOT leaving them on 24/7?
>>
>> Depends on the circumstances.
>>
>>> If not, how can they make scientific
>>> comparisons of drive-bearing life?
>>
>> The viewpoint is generally based on experience with other mechanical
>> devices.
>>
>>> As long as the head isn't moving,
>>> bearing life seems to be the main concern.
>>
>> Even if the head is moving, bearing life is the main concern as far as
>> _wear_ goes. The heads run on an air bearing--the wear is negligible.
>>
>> However disk seldom die of bearing failure--generally the failure is a
>> crash or an electronics failure.
>>
>>> On a home PC left on all day
>>> it's far less likely that the drive will be doing anything but spinning
>>> at high RPM for no real reason.
>>
>> Maybe on _your_ system.
>>
>>> I've heard similar claims that the "shock" of turning on a light bulb
>>> is worse than leaving it on all the time. Usually those comments came
>>> as a way to excuse energy consumption after a debate on the merits of
>>> waste. In reality, bulbs have a finite hours rating and will burn out
>>> faster the longer they are left on, as long as they aren't flipped on
>>> and off as torture. CFL bulbs (w/ballast) don't like to be switched on
>>> and off quickly, but I can't imagine them burning out faster if you
>>> only cycle on/off once in 10 minutes or so.
>>
>> You ever notice how light bulbs generally blow when you turn them on, not
>> when they are just sitting there giving off light? It's called "thermal
>> shock" and it's a real phenomenon.
>>
>>> Would anyone claim that car wheel bearings get as much wear when you
>>> pull out of the driveway vs. a 500 mile nonstop trip? In that case, the
>>> "spin up" would be when you first move the car after sitting. What
>>> exactly causes the "big shock" when a hard drive spins up? The heat
>>> generated from constant spinning would seem to far outweigh it. Why
>>> does Windows have a "Turn off hard disks" feature in Power options if
>>> not to reduce bearing wear?
>>>
>>> If anyone has thorough technical articles on hard drive wear, please
>>> post. Specifically, what is so torturous about spinning up the drive,
>>> and how can that brief cycle be quantified, damage-wise against
>>> constant spinning with higher heat levels?
>>
>> The basic problem with any bearing is that at rest the mass supported by
>> the bearing causes the rotating assembly to sink though the lubricant
>> until it
>> is touching something solid. When the device of whatever kind is
>> started, there is a period before the lubricating film reestablishes
>> itself in which
>> there is metal-to-metal contact. Thus most of the wear occurs at
>> startup. This is exacerbated by the fact that the lubricant is cold and
>> thus does not flow well.
>>
>> The "heat generated from constant spinning", assuming that the drive is
>> not being operated outside its rated temperature range, has negligible
>> effect on the durability of the mechanical components--it would have more
>> effect on the electronics but the electronic components are outside the
>> capsule.
>
> John... sounds like you know what you're talking about. So my question is:
> In my Windows power scheme I have for years selected "Turn Off Hard Disks
> = after 3 hours". I have never noticed this actually happening. Sounds
> like you would suggest turning this option off.
> Possibly I don't notice the drive spinning down is that I seem to have
> fairly constant network activity. I have a DU meter that monitors the
> network and it pops up more often than every 3 hours. So maybe my 2 drives
> are not "turning off".
In practical terms it makes little difference. Disks are rated for a certain
large number of start-stop cycles--WD Raptors for example are rated for
20,000. If you're running a server it's unlikely that it's ever going to
be idle long enough for the disks to power down.
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
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