Re: Life of CD install disks
- From: Mike Luther <mike.luther@xxxxxxxxxx>
- Date: Sat, 22 Sep 2007 14:10:11 +0000
Simple very effective solution Bob ..
Bob Eager wrote:
But beware the power surge that kills both disks...!
Use a mobile drive tray for the backup disk. I've been doing this with Jan's DFSEE for a long time now on several boxes. That on top of UPS capability. As well, though most won't go this far, the mission critical stuff is in rack mount industrial relay rack full transformer cases for lightning surge protection on beyond the transformer based APC UPS RM units.
The details on how to really protect your site and data are below for those who want all the messy text.
At my ham radio site with the big low band phased vertical arrays I take an average of at least one direct hit a year there plus LOTS more power line hits. The proper surge suppression work is sure there on all the tower lines, as well as the interface at the entry points. If you really understand the arena of how lightning works you *NEVER* depend on the conventional surge suppressors for actual lightning protection, especially where switching type power supplies are involved like we see virtually everywhere in the computer and games game and so on! The shunt diodes in them do clamp the lightning surge to the green wire ground. But because lightning is *NOT* electricity in the conventional sense of the word, but is a gigantic strong radio wave, it doesn't travel inside the ground wire or any wire.
It travels on the surface of metal seeking ground. As a radio wave, it has a period length that varies during the milliseconds lifetime of the stroke as the frequency of the stroke changes. The peak voltage point vs. the peak current point are a quarter wave apart on the surface of the metal carrying the stroke. That can and often does vary between a 'normal' maximum of about 250 feet per quarter wave down to only a six or eight foot minimum length! All during just one hit.
That is the reason that inside a home or building, we often see a TV set or whatever blown to bits, but eight or ten feet down the same general wire area in the power loom of the site, other electronic goodies are still working!
More important, for the surge protector failure to keep your switching power supply stuff working, the surge protector diodes do clamp the surge to the ground. But because the neutral ground on the power line may *NOT* be ground at all due to the surface flow and min-max voltage and current areas in the whole scenario, the lightning travels the REVERSE direction down to the computer stuff plugged into them on the green ground line to your prized boxes with your life time worth of work! There, because they are equipped with switching power supplies for the most part, what happens is on a 12 volt DC output line system, the peak voltage during the strike will actually produce the 120 volt over 12 volt ratio reduction on the ground foils of the whole board complex in the box of ..
say .. 400 volts on the ground foils of the 4000 volt spike.
BLAM .. your whole life is gone bye - bye.
Without a separate tape .. or drive tray box.
Physically removed from the grid.
Enter pig iron old time transformers. The lightning surge, as a radio wave issue, can't go through the pig iron induction transfer process for the old linear power supply stuff. Nor the really good UPS power supply units that use them. Nor an actual pig iron isolation transformer for the whole mission critical computer table if that is the way you want to go. And YES, the conventional surge protectors DO have use for the still found power line voltage surges for things other than lightning which go wrong from time to time. And for phone line surges for your modem lines as well.
Lastly, the final step in total protection for the site is the ring of wire at surface level on the ground around the building, together with the short little ground mat grid of wires which protrude out along the ground for six or eight feet away from the main ring. Since lightning is surface conductor oriented, it is really trying to sink itself to the SURFACE of the ground during the strike. A regular NEMA ground rod is really relatively useless for this. We carry the strike current out to the wire ring around the place, then deliberately to the surface at several places to properly sink the surge where it is going - no matter what else - is in the way.
Beyond this. things can and do still go wrong for surges from the power grid that may not be lightning caused, but may result from transformer and capacitor and circuit breaker issues far away from your prized data. So conventional surge suppression gear is still needed.
And there is one more huge issue which is involved in this as well that few people are really thinking about in keeping us running in our electronic age of whatever.
Just as in a nuclear device explosion up in the sky even a thousand miles away that generates an EMP pulse at say 30,000,000 volts per meter traveling at the speed of light, taking out virtually ALL wire connected computer and electronic gear for the thousand mile foot print around it, from the pulse induced electrical shock. so does lightning do this near it locally!
Even in a well designed protected site, the DC voltage spike so produced from the bolt that hit your neighbor's house still needs the in-site surge protection from convention protection devices .. even with the thought of hosting a neat pig iron protection plan for the really mission critical stuff.
The above is very solid information. If you have very mission critical data and aren't operating from an underground bunker with real surface interface protection, the above is all very real solid help.
As well as the ultimate way to instantly be back up from the mobile drive tray game. Which if it is really critical, you could do as a fiber connected LAN operation, via the OS/2 file mirroring technique at a completely separate site location in near real time, I guess.
Just trying to help here as an old Narte master broadcast engineer from long ago and far away and getting hit dozens of times a year at old WTAW radio in Aggieland as their Chief Engineer in the 1960's. Properly protected it's actually fun to look out the window at the tower and see the up arching fingers on the tower seeking to connect with the clouds for the strike. It does move from the ground up to the clouds for the initial hit much of the time.
Plus as far as I know, the longest recorded strike travel in clear air that killed people is about twenty miles. Fully documented on death on a golf course up in Colorado from a recorded bolt in a thunderstorm. With not a cloud in the sky anywhere near the golf course. So I wouldn't count on a mobile drive tray .. or a USB stick surviving either if not put in a safe place as well under the worst of time. Wince.
--> Sleep well; OS2's still awake! ;)
- Re: Life of CD install disks
- From: Bob Eager
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