I’ve worked in a datacenter as a computer operator since '89. When I started we had several Data General machines and two soon to be retired IBM Series Ones which had big red STOP pull handles on them (the DGs did not).
Now we have a zSeries S/390 and two AS/400s (i.e. an all IBM shop) and the datacenter has several EMERGENCY STOP buttons across the room, I believe at IBM’s insistance.
My question is, why?!
Not only do I see no benefit to having big red kill switches, I see them as a huge liability. The last thing you would ever want to do is just kill the power to a running mainframe. Plus I really can’t see any circumstance where it would ever come up.
So are these a legacy from the past? If so, why were they needed (or even wanted) back then? Danger of electrocution?
One reason is for an electrical fire. The power densities in older computer equipment can be very high. Many of the power supplies could be used for arc welding in a pinch. There are also mechanical devices that could be dangerous if they failed in certain ways. Another reason is flooding. You want to be able to kill all power without doing it standing in a puddle of water.
Those beasties run on redundant power circuits, and draw a LOT of power. 50 amps of 208/240 3-phase power per frame is not uncommon. The battery backups also involve huge amounts of power - thousands of amps.
All of that power connected by multiple means makes a full power-off challenging. As **mks57 ** said, that stuff doesn’t want to be wet. Of course, there shouldn’t be any water in the datacenter, but all the CO2 or Halon in the world won’t keep things dry when the firefighters show up with water in their hoses.
BTW, IBM’s term for this is UEPO, or Unit Emergency Power Off. The remote panic switches in the room connect to the frame’s UEPO, and when activated, all power - AC mains and battery - is disconnected.
I didn’t know you were a computer operator. I thought your name was a quote from the O’Reilly-published Feuerstein book on PL/SQL programming, affectionately known as the Ant Book. In the introduction, the author spends a paragraph or two explaining what all-around sensible and prudent little chaps these tiny insects are, concluding with the interjection “Hail Ants!”
Or if the air conditioning maintenance guys show up to clean/service the units and don’t reconnect a hose properly before switching it back on :eek: . That scenario lead to News International having to buy a roomful of new gear a few years ago.
Ouch. And that, kids, is why air conditioning equipment should be under the floor or in another room.
FWIW, our datacenter standards don’t allow any water pipes in or above a machine room. No sewers, potable water, sprinkler lines, air conditioner drains - none.
Well, at one of my former work-places, the fire service (the site was big enough to have its own fire service) always insisted that the official procedures were followed in a fire drill - woe betide anyone who didn’t press the STOP buttons or, worse, go out of the cleanroom through the fire exit rather than the normal door. Management were aware that a 40-minute fire drill cost us two or three days of production, and budgeted for it - because, if the correct procedures weren’t followed, the fire service would call another drill on the following day, so we’d lose a full week of production instead.
The place shut down a couple of years back, for financial reasons.