BOFH and the VAX cluster bomb
So I'm having a quiet six pints after work - waiting for The PFY to join me so I can shout him a lager or two - when a geeky type from the Helldesk crawls over and introduces himself.
I'm momentarily taken aback by this blatant abuse of workplace hierarchical protocol, but this is shortly overcome by his intriguing question.
"I was just wondering," he burbles, "if you know of a way to fire protect some equipment I've got?"
"Fireproof?" I ask. "An unusual request. What sort of equipment precisely?"
"A vaxcluster," he burbles excitedly.
"A VAX Cluster?" I ask, suppressing a shudder.
"Yes, but not just any ordinary vaxcluster - it's a beowoulf cluster."
"A Vax Beowoulf cluster," I repeat, pausing momentarily to try and think of a sadder life form - coming up blank.
"Yes, I've got three Alphas, Two 11/780s, a 11/730 and four microvaxes."
"And I'm rebuilding an 8530 which I got from a company that was going to SCRAP it!"
"Shocking!" I concur, humouring him - figuring that anyone who would rebuild an 8530 in their own time is someone who needs gentle handling.. (and possibly locking up for a long, long time). "Although, TECHNICALLY the Alphas aren't actually VAXes, are they?"
"No!" he blurts, incorrectly identifying me as a fellow Digital geek. "HOWEVER, they're early Alphas, which were the most backwardly compatible."
"I think you'll find that most of that gear is fairly backward," I murmur.
"I said I think you'll find that you're going to need fairly hefty fireproofing. What sort of room are they in?" I ask, mentally picturing the hottest, noisiest, most cramped double bedsit in the world.
"Well it's a perk of a part-time job I have looking after a standby datacentre - they let me run some of my machines there in return for me keeping an eye on the place.
"Right, I see. So there's no space problems. And given the machine's age, I assume you're worrying about thermal shock?
"Is the cluster doing anything important?"
"Well it's been calculating Pi to a new record of decimal places for almost a year now."
"So you don't want to take it down to install the fire protection?"
Our conversation is interrupted by the arrival of The PFY, so I get the Helldesk geek back over with a quick wave and ask him to explain his dilemma, telling him The PFY is the brains behind our infrastructure protection systems.
As the problem unfolds The PFY's eyes light up in anticipation.
"I suggest you use a liquid extinguisher, stored at room temperature," The PFY comments as turns from the bar with a drink for me and the Helldesk geek.
"No - Gas systems introduce thermal shock from their expansion - law of thermodynamics. Besides, they're hellishly expensive. However, a liquid coolant/extinguisher doesn't expand, and so can be kept at the same temperature as the equipment."
"I see. And what coolant do you suggest, water?"
"No, water has a problem in that it can actually act as an oxidant in very hot fires involving metals like magnesium, etc, some of which are used in computing."
"So what coolant?"
"Well, recent thinking seems to centre around a semi-viscous liquid like an oil."
"Yes - because oil has a very low heating coefficient."
"It takes ages to get oils to change temperatures, which makes them ideal for extinguishers."
"Of course! Think about it. How long does it take to boil a jug?"
"About five minutes."
"And how long does it take your chippy to warm up their vat?"
"I don't know."
"Well it takes about one and a half hours - see my point?"
"It takes a lot longer to heat vat oil up than the water in your jug. And you know why?"
"Because the vat's about 100 times the size of my jug?"
"NO, because oil has a lower heating coefficient!"
"Oh, I see. So what oil is commonly used?"
"Generally, Industrial Diesel."
"DIESEL OIL!?!! But that's flammable!!" the geek cries.
"Only under very particular circumstances," The PFY responds calmly, plying the geek with yet another drink, "generally very high pressure as well as extreme heat. Neither of which you'll get in a computing environment."
"I don't understand," the geek responds, dubiously.
"Do you know how a diesel engine works?"
"Like a car engine?"
"Not at all! Diesel has such a low octane that the engine actually has to pressurise the stuff to make it ignite. AND the engine has to have heat from a glow plug to actually get the pressurised stuff to burn!"
"Of course. hy do you think most of the world's cars run on petrol?"
"And it won't catch fire in computers?"
"It hasn't in ours, and we've been using it for over a year now."
"Of course, what do you think those drums of diesel in the store are for?"
"Goodness no! You wouldn't run a generator on Industrial diesel! It's crap. You'd be better running it on petrol like we do"
"You run your diesel generator on petrol?"
"Uhuh, and we use the diesel for our fire extinguishers. In fact, I could probably give you a barrel as we only keep it in case of a leak in the system."
"I don't think I need it - we have a generator in the datacenter which I could refill with petrol, and use the diesel of!"
"Right! Where is this datacentre?"
"It's a couple of blocks away, in the basement of that large insurance building."
"An Insurance building" The PFY mouths thoughtfully. "Tell you what - why don't you shoot there and set it all up and we could help you commission it once we've had our dinner!"
"Ok!" The geek chirps, slipping off quickly.
"Couple more pints before we head over?" The PFY asks.
"Yeah, I spose I could fit them in. And remind me to pick up your birthday present on the way over."
"What, the latest Viz mag?" he asks, recounting last year's present.
"I was thinking a packet of marshmallows?"
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