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Power Distribution in a Datacenter?
d00dman asks: "I work for a colocation reseller. We don't own our datacenter, we lease cage space and with it we get an array of 30amp and 15amp power circuits. My problem is, inside of the cage we need to do our own power distribution. We have around 50 hosts in the facility, and are growing quickly. We need to add another 20 or so hosts in coming month. We are looking for a simple, scalable, and even power distribution method. As always, money IS an object. Right now we have a group of UPS's with power strips plugged into each. While this was sufficient for as many as 30 hosts, its starting to become a bit of a mess. Does anyone have any advice to offer...any creative tricks?"
...But have you considered moving to a datacenter which provides conditioned power? After all, stacking UPS' in your rack is not very efficient. Especially when you're running powerstrips off them.
Many datacenters now provide fully conditioned, bus-sized UPS-backed power. Some even let you control individual power outlets from an SSL/password-protected web interface (Which is extremely useful if/when a server hard locks). Even if the datacenter doesn't provide the web-based outlet management, you can pick up a 1u, 8-outlet APC power switch for $300. 5 of them would provide power for the whole rack (Assuming single power supply), and only cost $500.
- James
(Simple Solution - APC Power StruXure)
First off, get rid of the stand-alone UPS systems. They are inefficient and not reliable from a system standpoint. You are much better off with a single 30kW unit rather than ten or twenty 1,000VA units. With single UPS, it is easy to either install a local panelboard (US), or a busbar distribution system (UK).
Second, anything that you do to enhance flexibility will compromise reliability. If that is an acceptable risk they go ahead and do something modular.
Given these constraints, a 30kW UPS is 100A or so three phase, 208V or 150A single-phase 208V. 120V would not be appropriate; 480V is a cheaper input feeder, more hassle for bypass.
The best solution might be to go the traditional panelboard route, and run branch circuits to all your equipment in liquidtight flexible non-metalic conduit (the blue stuff).
Alternately, you can install a 100A plug-in busbar the length of your cage and tap off 30A, 208V, 1PH for each rack. They are designed for light industrial applications, but work pretty well if you can sacrifice on reliability.
The APC solution is neat because you don't need an electrician, and it is all modular. Might not be as flexible as the component route, but it works. I think it includes managed outlets in the racks as well.
In the context of a good datacenter conditioned power also implies building wide UPS and multiple backup generator systems.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
A "Double-Conversion" UPS provides power conditioning and battery backup. Alternately, a UPS with internal choke can provide conditioning without full double-conversion. A breadbox-style UPS is usually just a single-conversion device, which works as you describe.
Usually people plug small systems in for the wrong reasons... 'what if this huge building system that is maintained regularly "breaks?" Good think I have this little box here that I've been using for the past five years without any problems..!' or 'I want to be able to move the server around the room without unplugging it' nonsense.
There are very real problems associated with plugging the little shits into a large system; the cheap inverters have trouble tracking and can create all kinds of problems.
Also, always remember that the sealed batteries only last 3-5 years if you are lucky!