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Comment Re:Simplify the problem, use a metrics based appro (Score 1) 64

Convert your metrics into time units so you can say something like "I need 6 CPU/S per 100 users at nor more that 80% utilization" . The math is less weird than trying to work in percentages of something you're going to replace with a CPU that's 12% faster (;-))

Comment For anything expen$sive, we use TQ (Score 5, Interesting) 64

I used to work for the (late, lamented) Sun Microsystems, and when we needed to give a credible answer to a price-sensitive customer, we used Teamquest Model. It pulls time-based info out of production-systems stats, so it doesn't add to the load, and then off-line does a classic queuing-system model of the system, working all in time units. That then allows the customer (really meaning me!) to ask what to expect from some specific configuration, and compare different systems for their price-performance tradeoffs.

For common setups, we have spreadsheets based on what Model said, so the salespeople typically don't know there's a cool mathematical model behind the scenes (;-)) That's probably true of other vendors who use TQ models: it runs on anything modern, so lots of vendors use it.

I have nothing to do with the company: they just allowed me to save $1.2 million once for a new datacenter, so I'm really really impressed by them.


Comment It takes four magic words in the first sentence (Score 2) 479

Hi, I'm an enraged customer, I'd like to speak to your escalations manager.

It helps to say that in the kindest possible tone, too.

"Escalation manager" is the normal term for someone who talks to "enraged customers". It may or may not be what your ISP uses, but the two phrases in the same sentence tend to get you to the right manager.

Did escalations for a while at Sun, some of the problems were real fun. Others weren't.

Comment Re:"stealing just like stealing anything else" (Score 1) 408

Imagine if a company in Virginia had, in their terms and conditions, a line prohibiting a citizen of Massachusetts from purchasing their product or service? One requiring they buy it from a specified licencee in Mass?

Can you say "criminal conspiracy in restraint of trade" ?

Comment Epic fail: someone always matches (Score 2, Interesting) 129

This scheme will work for one branch in Lesser Nowhere, Sechwan Province, with a finite and small set of pictures, and a small number of crooks. Once the number of faces increases, the probability of a false positive explodes, roughly as (N 2) (select every two out of N), where N is the size of the pools of pictures + the person being scanned.

The well-known example is the "birthday paradox", in which twenty-three people at a party increases the probability of two of them having the same birthday to fifty-fifty. That particular case was because the actual probability was multiplied by (25 2) = 25! / ((25-2)! * 2!) = 6900 comparisons being made, times 1/365 chances of a hit.

The German federal security service considered using one of my then employer's recognizers for airports to catch terrorists, but ended up facing the problem of accusing grandma of being part of the Bader-Meinhoff gang (;-)) No matter how accurate we were, a few more people in the pool would give us false positives. We'd need roughly an accuracy of 99.9 followed by roughly as many decimal places of 9s as there were powers of ten of people.


Comment many recruiters are hired off the street (Score 1) 227

A sister company did recruiting, and a then colleague said "I asked for a MVS and Unix person in a particular state with experience in a package", and got hundreds of names, none of whom knew all those things". The didn't know the difference between "and" (3 candidates) and "or" (3000 unqualified candidates). I still get requests for things I only ever did once, with co-requisites of things I've never done...

Comment Re:Help me out here a little... (Score 1) 533

I think you'll find that electricity won't flow out of the solar supplier if the voltage in the line is at 120v, as there's nowhere with a lower voltage for it to flow to. Anyone who draws current from the system creates a region of lower voltage, and current flows toward them until the voltage is the same everywhere. Think of it electricity as being rather like water in a sealed watertower: no more flows in if it's full, plenty flows out if someone lowers the pressure by opening a tap.

Therefor the spike from all the solar installations just offers more power. If no one takes it, current doesn't flow, the solar folks' ammeters don't budge and they don't get paid by the power distribution company. If somebody turns on a light, current flows, and some supplier's ammeter moves, usually a supplier close to the lightbulb. Ditto the consumer's ammeter, what we call the "electric meter"

Comment They have to put in safety equipment in any case (Score 4, Interesting) 533

To connect a power source to the grid, there has to be a cutoff that disconnects it when the grid voltage drops to zero due to, for example, a tree falling and shorting it to ground. If there isn't a cutoff
  • - the grid sucks all your power and probably blows your fuses and/or rectifier diodes, and
  • - the hydro guy who expects to be handing a dead line suddenly has it jump to 110 or 220V, the instant he lifts it off ground.

Linemen don't like becoming part of the circuits, so they successfully called for the disconnect-if-zero laws.

Power companies (at least in Canada and large parts of the world) already have equipment to deal with the fact that the power can flow both ways. In fact, claiming they don't have equipment is only true IFF the power companies are the ones who like electrocuting their employees (;-))

If mathematically you end up with the wrong answer, try multiplying by the page number.