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Fascinating story -- the vacuum tubes in the computer drew so much current when it was switched on, that they had to wait for the bakery down the street to turn

Fascinating story -- the vacuum tubes in the computer drew so much current when it was switched on, that they had to wait for the bakery down the street to turn off its ovens before they powered the computer on for the day. Otherwise they'd blow up a transformer.

rbanffy 8y ago
I once had a bug report where a client was having boot failures seemingly at random - machines would not come up and be detected by the management software. It turned out they were powering up all machines at the same time and that caused a low voltage on the power rail.
- walrus01 8y ago
  On big servers (4RU, quad socket xeon size), BIOS features exist specifically to deal with this in electricity outage situations. Most people will leave the option set to "last state" for power recovery, meaning that after total loss of AC power, the server will attempt to return itself to the last operating state, typically on. Problem is when you have dozens of such servers, the inrush current if they all try to power on at once is huge. So there's a second BIOS option, allowing you to set a custom time-delay between return of AC power and when the system attempts to start, or to choose a random start delay between 1 and 30 seconds so that a whole series of machines don't all try to start at precisely the same time.
  - sevensor 8y ago
    I don't know how data centers are set up, so this is a comment made in ignorance: I'm surprised this isn't built into the electrical service for the rack. Only distantly related: I kept tripping a breaker in my kitchen while making breakfast. It took me the longest time to figure out that I could run my toaster and coffeemaker at the same time, but if the fridge compressor kicked on while I was doing that, it would overload the circuit. It took me so long to figure out what was going on because I was always dealing with this situation before I'd had my coffee.
    - rbanffy 8y ago
      The solution, as always, is to have more coffee. Had you increased the odds of having all three on, by having more coffee, you'd be able to observe it with a chemically alert brain.

rbanffy 8y ago

I once had a bug report where a client was having boot failures seemingly at random - machines would not come up and be detected by the management software. It turned out they were powering up all machines at the same time and that caused a low voltage on the power rail.

walrus01 8y ago
On big servers (4RU, quad socket xeon size), BIOS features exist specifically to deal with this in electricity outage situations. Most people will leave the option set to "last state" for power recovery, meaning that after total loss of AC power, the server will attempt to return itself to the last operating state, typically on. Problem is when you have dozens of such servers, the inrush current if they all try to power on at once is huge. So there's a second BIOS option, allowing you to set a custom time-delay between return of AC power and when the system attempts to start, or to choose a random start delay between 1 and 30 seconds so that a whole series of machines don't all try to start at precisely the same time.
- sevensor 8y ago
  I don't know how data centers are set up, so this is a comment made in ignorance: I'm surprised this isn't built into the electrical service for the rack. Only distantly related: I kept tripping a breaker in my kitchen while making breakfast. It took me the longest time to figure out that I could run my toaster and coffeemaker at the same time, but if the fridge compressor kicked on while I was doing that, it would overload the circuit. It took me so long to figure out what was going on because I was always dealing with this situation before I'd had my coffee.
  - rbanffy 8y ago
    The solution, as always, is to have more coffee. Had you increased the odds of having all three on, by having more coffee, you'd be able to observe it with a chemically alert brain.