[Beowulf] Re: Cooling vs HW replacement

[Joel Jaeggli]

On Fri, 21 Jan 2005, Robert G. Brown wrote:

> On Fri, 21 Jan 2005, David Mathog wrote:
>
>>> 	2. higher reliability - typically 1.2-1.4M hours, and usually
>>> 	specified under higher load.  this is a very fuzzy area, since
>>> 	commodity disks often quote 1Mhr under "lower" load.
>>
>> Exactly.  It's very, very hard to figure out just how much reliability
>> one is trading for the lower price.  Anecdotally, for heavy disk
>> usage, it's apparently a lot.  Anecdotally, for low disk usuage,
>> ATA disks aren't all that reliable either.
>
> Has anyone observed that a megahour is 114 years?  Has anyone observed
> that this is so ludicrous a figure as to be totally meaningless?  Show
> me a single disk on the planet that will run, under load, for a mere two
> decades and I'll bow down before it and start sacrificing chickens.

mtbf is an estimate of how often failure should occur in the disks if you 
run them for their service life and replace them. since disk vendors don't 
publish service life (one assumes it's shorter than the warranty) it's 
kind of a meaningless number. I guess if you have a million disks you 
should lose about 1 per hour.

> Humans don't live a megahour MTBF.  Disks damn sure don't.
>
>   rgb
>
>

-- 
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Joel Jaeggli  	       Unix Consulting 	       joelja at darkwing.uoregon.edu 
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