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Are you prepared for a power outage?
A momentary glitch that would hold up a line of customers with 10 minutes of restarting doesn't even faze us. Also, it really wows the customers to see the equipment running smoothly when the rest of the city goes dark.
Be sure to test the capacity before you need it. A CRT monitor almost needs its own UPS. Also, don't neglect things like modem/router, which I often have in a different location than the computers themselves. A separate UPS for the credit card terminal, register, and other office essentials keeps those going too.
Important caveat: Laser printers usually overwhelm a UPS once out of standby. Test everything before you *need* it!
He did use the Honda generator once. They lost power to his neighborhood due to a construction accident. The neighbor across the street noticed the generator running, and asked if he could plug into it to stir paint with an electric drill. I had to explain to him later that small generators aren't intended to run inductive loads...
I'd avoid cheapie UPSs. They typically have only enough backup time to save your work and shut down. And they can be glitchy. Look for one with a sine-wave output. What you don't need is "on line". An "on line" UPS runs your equipment off the battery at all times. The conversion in inefficient, though, and you will use 20-50% more power. Good UPSs will switch from line to inverter power in less than 1mSec, and have sufficient reactive storage to bridge much more than the 1mSec.
I also put 1 redundant power supply in each server for failover
You can get an additional mode of failure protection "for free" when using redundant power supplies. In most cases, each of the redundant power supplies has a seperate AC connector coming in.
In a good data center, you have two power sources coming into your cabinet - they should be run off of seperate UPS's and/or seperate AC supplies to the building.
Wire each power supply in your redundant servers to the seperate power sources.
There are also distribution panels that will do this for you in the case of servers or other equipment that have only a single power supply. You run two power sources into the distribution panel, and one power line comes out. It switches over automatically if power is lost from one of the sources.
Most good UPS's self-test, so you don't get any choice. Mine "pulls the plug" for a few seconds once a day.
The chicken's way out is to put your machine(s) on the BIOS setup screen and pull the plug.
Most of the Good UPS software is not really approrpraite for hardened web servers. I'v had a long standing problem with a major vendor who has put so much junk in the UPS software it requires IIS, Java and outbound http just to work!
In an ideal world I'd have separate UPS for each power supply, but its all down to cost. The 2 power suplies per server gives failover if one blows, but yeah they are both on one UPS.
they should be run off of seperate UPS's and/or seperate AC supplies to the building.
Let me clarify what I meant here.
A good data center should provide UPS-backed power to your cabinet. The best ones will provide redundant power to your cabinet - two power feeds, each run off of a seperate UPS and, often, run from seperate power feeds into the building from seperate transformers. You should also check on the existence of a generator, generator capacity, and configuration (are there also redundant generators? This is probably much less common.)
If you need to supply your own UPS, then I agree that two of them would be overkill. For one thing, you probably would have no Internet connectivity in case of power loss, if the facility lacks UPS backup. (Though in some cases they might backup their own equipment, but not customer equipment.) So, your UPS would serve mainly to get your equipment shut-down cleanly in case of a loss of power.
Anyway, what I was suggesting is that IF your data center supplies redundant power, and you have redundant power supplies, make sure to take advantage of the redundant power, by plugging the power supplies into seperate supply rails.