Yesterday, I was in my local computer retailer, and was looking at hard
The older "physical" bearing drives (left over, not newly produced)
still indicated the 3 year warranty on them.
The same brand sporting the new "ultra quiet" liquid or fluid bearing
indicated "one year warranty".
Now, I don't know if this is indicative of:
1) the expected lifespan of the liquid bearing drive is lower
2) the company got so badly burned by the number of returns of the
previous standard bearing drives that they decided to cut their losses
on the new ones, even if they are equivalent or better in reliability
3) new "industry standard" (read: this is how we keep costs down, by
limiting our liability to warranty replacements).
Julian Robinson wrote:
>>>Well, the one thing you can say with absolutely certainty is
>>>that the MTBF is not based on observational data.
>>I can say with relative certainly that you are wrong.
> Purist statistical theory aside, the MTBF (IF it was measured in real-life
> conditions) does give you a very useful and practical estimate of how long
> you can expect your drive to last. And even in the purist domain, with the
> given 300,000 hour example you can say accurately that the chance of a
> drive failing in a given 12 month period is around 3% which is extremely
> useful info.
> This doesn't take into account the bathtub effect mentioned.
> But the real trap is that the MTBF's are not measured in real life
> conditions, which is I suggest why observation would not support the
> 300,000 figure. Real life includes power surges and spikes, physical bumps
> and electrical problems related to people "playing" with their systems -
> installing, testing and uninstalling, as well as software-related and often
> recoverable failures like corruption of your master boot record.
> So when thinking about backup strategies, you need to consider the 3%
> "native" chance of a drive failing in any year, increased, (possibly
> greatly) by any physical, electrical or excess start-up stress. All in all
> a figure of 5 to 10% per year seems likely in average circumstances, and
> that is pretty well I think what we see.
> I leave mine on 24/7 and have had no probs at all with 6 disks over 6
> years, until ... the other day when 2 died. I suspect lightning related
> surges (through the UPS/surge protector??Hmmm). I wasn't backed up
> properly (only one disk to another and a few semi-random CD's) so am
> currently out to the forensic disc doctors. Damn.
>>In the intersts of keeping an interesting thread going here are some typical
>>reliability figures for hard drives:
>>Mean time Between Failure 300,000 hours (ie one failure every 34 years)
>>Start/stops (at 40 deg C) 40,000
>>On the basis of those figures I turned HD power management off on my PC. I
>>was finding the disks were getting turned off maybe twenty times a day,
>>which equates to one failure every 5 years or so.
> Canberra, Australia
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