Re: RAID Class Drives`

[Eric Shubert <ejs@shubes.net>]

Leslie Rhorer wrote:
>> -----Original Message-----
>> From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
>> owner@vger.kernel.org] On Behalf Of Aryeh Gregor
>> Sent: Friday, March 19, 2010 11:43 AM
>> To: John Robinson
>> Cc: Joachim Otahal; linux-raid@vger.kernel.org
>> Subject: Re: RAID Class Drives`
>>
>> On Fri, Mar 19, 2010 at 4:15 AM, John Robinson
>> <john.robinson@anonymous.org.uk> wrote:
>>> Do you have a reference for this? Most drives' operating temperature
>> range
>>> is specified up to 55°C, sometimes higher for enterprise drives, without
>> any
>>> indication (apart from common sense perhaps) that running them this hot
>>> reduces lifespan.
>> Google's study of >100,000 disks over 9 months or so
>> <http://labs.google.com/papers/disk_failures.html> suggests that
>> hotter drives don't fail much more often:
>>
>> ". . . failures do not increase when the average temperature
>> increases. In fact, there is a clear trend showing that lower
>> temperatures are associated with higher failure rates.  Only at very
>> high temperatures is there a slight reversal of this trend." (page 5
>> of PDF)
>>
>> "We can conclude that at moderate temperature ranges it is likely that
>> there are other effects which affect failure rates much more strongly
>> than temperatures do." (page 6)
>>
>> They were using SATA and PATA consumer drives, 5400 RPM to 7200 RPM,
>> 80 to 400 GB, put into production in or after 2001 (from page 3).
> 
> 	First of all, not what they call "high" temperatures in the paper
> are not really very high.  Eighty C is roughly the boiling point of Ethyl
> Alcohol, and in human terms this is considered quite hot.  Immersion of body
> tissues in a large volume of 80C water for several seconds will result in
> moderately severe burns.  For most mechanical systems however, 80C is not
> particularly hot.  Many solid state electronics systems can withstand 80C
> internal temperatures indefinitely.  An average healthy adult human being
> has a body core temperature of 37C, and a device with a 40C surface
> temperature is barely warm to the touch.  It is not hot. Unless one employs
> a refrigerated fluid cooling system or a Peltier junction to actively cool
> it, no drive system is ever going to be less than 30C if the room
> temperature is anything other than uncomfortably cold.  It's rather cold in
> my house right now, because I have the heat shut off to save money, yet the
> coolest drive in my arrays - which have very effective forced air systems
> built in to them - are 31C.  Most are over 33C by a wide margin.  Come
> summer, all of them will be over 40C.
> 
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I had a few drives running at about 55C for a couple years, with no 
failures (knock wood). These were used drives before being put into that 
environment, so they arguably had already survived the "infant mortality 
syndrome" that the google study identified. Would I recommend running 
drives at 55C? No, but I wouldn't be too concerned about it either.

FWIW.

-- 
-Eric 'shubes'

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