Re: What Size Partitions for XP and Linux?
From: Juhan Leemet (juhan_at_logicognosis.com)
Date: 10/13/04
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Date: Wed, 13 Oct 2004 00:57:32 -0200
On Mon, 11 Oct 2004 11:56:29 -0400, Jean-David Beyer wrote:
> Harold Stevens wrote:
>> In <10mksoa9ufja4cc@corp.supernews.com>, Jean-David Beyer:
>> [Snip...]
>>>But I do not see how, other than spike elimination, a UPS could protect
>>>disk drives and other stuff after the power supply.
>>
>> My understanding (I'm certainly no expert) is that transient spikes might
>> be especially bad on electromechanics of drive motors and head servos, in
>> addition to being a Really Bad Idea (tm) for electronics generally.
>>
>> Not to say it's a fact, or relevant today, or that I'm even recalling the
>> vendor hype correctly. :)
>>
>> Anyway, I think we agree most UPS are worth a serious look today.
>>
> I used to design electronic equipment, way back in vacuum-tube days up
> until and including the small scale integrated circuit days, both analog
> and digital systems. If the power supply is any good, the spikes, etc.,
> will never get further than the input circuits of the power supply since
> the stuff is rectified, filtered, chopped to a form of AC, transformed
> into the needed voltages, rectified again, filtered again, voltages
> electronically regulated, etc. So the spikes should pretty well be
> eliminated by the time they input power is rectified and filtered the
> first time. After chopping, transforming, rectifying again, filtering
> again, etc., there should be essentially no noise left.
>
> The power supply, absent a well designed surge protector, will take the
> beating. Then only time a surge should hurt anything other than the power
> supply is if the surge is so large that it fries the power supply itself.
> Such surges are not unknown (nearby lightning strikes, trees falling on
> power lines connecting the primary (4800 volts in my neighbor hood) power
> into the secondary (120/220 volt) circuits, and such. For that, your
> insurance should take care of things.
Sounds like you have much more (relevant) experience than I do. However,
I am an EE who has designed and build some stuff, including hybrid
(analog & digital) instrumentation and have dealt with spikes.
I think it might also be possible for a big spike to be capacitively
coupled right through everything, before power supply regulators can
react. They are after all band limited to prevent oscillation. Generally,
for electronics (dunno about rotating machinery, like disk motors) it is
spikes that cause failures. I would have thought that the mechanical
inertia of HD motors would prevent even spikes from having significant
effect on bearings, motors, or head flying height, but I have not done any
research on it. I would like to understand the postulated failure
mechanism(s). At this point I might concede that it is possible (tho
unlikely?). No argument about UPS being a good idea.
p.s. At one point I was trying to diagnose a low signal level video
amplifier on a thermal imaging infra red-camera. Big electro-mechanical
beast with detector cooled with liquid nitrogen. At one site there were
big spikes in the signal and I could not figure out where they came from,
and couldn't suppress them without blurring the image. There was
construction going on in the building. I came to the conclusion that
someone had a high power solid state motor controller somewhere in the
power distribution grid, and their "hash" was coming through to this
particular power circuit as well. The instrument maker (in Sweden) may
have assumed cleaner power. Apparently in Europe it is your responsibility
not to put any noise on the power lines. This was a long time ago before
affordable UPS and power conditioning. So, I have seen stuff "get thru".
-- Juhan Leemet Logicognosis, Inc.
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