[huskerlug] Re: Installing Knoppix to hard-drive
- From: GreyGeek <jkreps@xxxxxxxxxx>
- To: huskerlug@xxxxxxxxxxxxx
- Date: Wed, 14 Feb 2007 19:33:43 -0600
http://www.datarecovery.com.sg/data_recovery/disk_drive_mean_time_failure.htm
*MTBF of a Disk Drive*
MTBF stands for "mean time between failures,". It is the average elapsed
time that passes before a failure occurs in a batch of drives under
intense test conditions.
However, a brand XYZ harddisk with a MTBF rating of 1 million hour does
not mean that the average unit will run for 114 years before it fails.
In fact, MTBF of a drive is obtained by multiplying a large quantity of
the drives (few hundreds or thousands) with the number of hours running
before experiencing a failure in the batch. For example, when a disk
manufacturer batch tested 1500 units of hard disk and achieved an
average of 30 days operation out of the batch between each individual
unit failure, then the MTBF of the disk is 1500 x 30 x 24 hours = 1
million hours.
I was expressing, poorly, four situations:
1) Drive is spinning all the time while it is on, and is left on
continuously.
2) Drive is turned on and off frequently.... say 3 or 4 times a day.
3) Drive spins down and stops spinning for long periods but the
electronics stays on
4) Drive spins down to a stop, and then spins up again for a few
moments, then spins down...
#1 Is easiest on the electronics but wears out the mechanical parts the
quickest. This drive may fail because of bearing failure.
#2 Is hardest on the electronics because of surge currents and voltages
during startup and shut down. This drive is prone to electronic failure.
#3 This HD may last the longest because the electronics stays on, but
the disk isn't spinning as much as #1
#4 This HD may experience electronic failure as quickly as #2 because
spinning up disks creates a current spike, which can also cause spike
voltages.
Add to this the fact that the electronic parts on the drive may have a
safety factor of 1.2 instead of 2x. If a circuit has a maximum voltage
peak of, say 12v, a capacitor should be rated at 24 volts. Cheap
equipment would use a 14 or 15v rating. As resistors with the same
rating over heat they vaporise organic binding agents, causing a change
in the resistance, which changes the voltage and current, which may have
a detrimental effect on other parts. Good designs include safety
factors which prevent the electrical base lines of voltage and current
from changing as the parts age.
Paul Andrews wrote:
> I'm confused. You say the opposite things in your statement. I always
> figured hard drives are essentially an electric motor, which typically (if
> it avoids over heating/ceasing/damage) can essentially run forever... I
> know, not forever, but longer than five years, and it's because it has to
> "spin down" sometimes (read: shutdowns of computer in my case) and then spin
> up again when the computer is booted where the "damage" comes in.
> A similar thing is seen in florescent lights. They will run much longer if
> you just leave them on continuously. But, if you turn them on and off
> frequently, they burn out much quicker.
>
> Perhaps I'm wrong, but that's what I always figured (and why I leave my
> computer on all the time).
>
> Paul
>
> On 2/12/07, GreyGeek <jkreps@xxxxxxxxxx> wrote:
>
>> Oh, I forgot...
>> The typical Mean Time Between Failure (mtbf) is 50,000 hrs of continuous
>> use, which is about five years.
>> If your HD spins down to "save" hours then the life of it may be more
>> than five years.
>> But, if your drive spins down and something causes it to spin up again
>> without requesting access to a file or directory, then the HD life may
>> be less than five years because spinning the drive up is the hardest
>> work the circuitry does.
>>
>>
>> GreyGeek wrote:
>>
>>> Check "top" and see how often "hald-addon-stor" fires in comparison to
>>> your drive light.
>>>
>>> Jim Worrest wrote:
>>>
>>>
>>>> Well, I've done this twice now, and it was basically ok, in fact I
>>>>
>> did this
>>
>>>> just lately over favor of the later version 5.1.1. I never noticed it
>>>>
>> much when
>>
>>>> I did it the first time, but it does it on that computer also, but on
>>>>
>> my last
>>
>>>> computer it is extremely noticable. It apparently accesses my hard
>>>>
>> drive once a
>>
>>>> second. Having my hard drive light blink once a second, makes me
>>>>
>> nervous. Why
>>
>>>> is my Knoppix/Debian doing this? Is there a way to stop this, short of
>>>>
>> putting
>>
>>>> on another distro, that is? How hard is it on the hard-drive? ---Jim
>>>>
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>>>>
>>>>
>>>>
>>>>
>>>
>> --
>> =========
>> GreyGeek
>> =========
>> Remember, a consumer is a customer with no choice.
>> DRM 'manages access' in the same way that jail 'manages freedom.'
>>
>>
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>>
>>
>>
>
>
>
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>
--
=========
GreyGeek
=========
Remember, a consumer is a customer with no choice.
DRM 'manages access' in the same way that jail 'manages freedom.'
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