[Beowulf] Re: ECC Memory and Job Failures (Huw Lynes)

Geoff Jacobs gdjacobs at gmail.com
Mon Apr 27 14:18:44 EDT 2009


Vincent Diepeveen wrote:
> 
> 
> 
> On Apr 24, 2009, at 4:20 AM, Robert G. Brown wrote:
> 
>> On Thu, 23 Apr 2009, John Hearns wrote:
>>
>>> Cosmic rays pass through us all the time - I don't know offhand the
>>> cosmic ray flux.
>>> Like Joe I did the cosmic muon lifetime experiment at University.
>>> I always wanted to do an undergraduate project using CMOS RAM as a
>>> radiation detector - read and write bit patterns to it, and see if the
>>> results match.
>>
>> Funny, I did it too.  One of my favorite undergrad experiments, proves
>> relativity theory, and there is the always muon catalyzed fusion to muse
>> over as well.
>>
>> I don't think memory is all that unstable, especially down where I live.
>> In Denver, maybe.  I think you need a lot of RAM, for a long time, to
>> see a lot of radiation induced errors, or a source of high energy
>> particles.
>>
> 
> Yeah usually it is a hardware or software bug.
> 
> However i noticed that if i saved my tapes (Ultrium2-200GB uncompressed,
> 400GB according to the salesman) at
> about 1 meter above the ground here, things go fine. Yet if i save them
> at 2nd floor here that is more risky.
> There is definitely more bitflips there. Now that is a lot closer to the
> 2 x 450 MVA powerlines, which are on average at a height of about 19
> meters above ground,
> a bit less when a lot of power is on 'em, as the cables tend to get very
> hot then.

Maybe the gravel for the concrete came from Gabon or something?

> Now on paper these powerlines are supposed to not radiate the ionising
> radiation very far. Say half a meter max (which doesn't
> really matter for life & death, as at 2 meters distance you're already
> dead in this wet climate).

Power lines don't produce ionizing radiation. The concern is ELF
(Extremely Low Frequency) radiation generated at the supply frequency of
the grid (60 Hz in North America, for example). ELF does not ionize.
Here, there's a wiki article and everything!

http://en.wikipedia.org/wiki/Extremely_low_frequency
http://en.wikipedia.org/wiki/Electromagnetic_radiation_and_health

> Would this measurement prove that ionising particles, which cause of
> course cancer, sometimes travel further away from
> these cables?

No ionization from the power line, see above.

> Thanks,
> Vincent
> 
>>    rgb

-- 
Geoffrey D. Jacobs
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