Battery Backup....

How much do I need?

[SEOMike]

I need a battery backup big enough to support 10 servers. How can I judge the power draw from each machine. (boxes only, no monitors) Does each one draw the maxium the power supply gives? Will a 3000va UPS suffice? Are there any good rules of thumb for battery backups?

I'm not looking for hours of UPS, just 5 or 10 minutes in the event there is a power flicker.

[anallawalla]

The APC site used to have a handy calculator where you could enter such details and it would tell you which UPS was the best.

[defanjos]

How can I judge the power draw from each machine

If you want to be 100% sure, get a clamp meter and test around the power cord - this will tell you exactly the power being consumed by each server (do it during power up, iddle, etc).

I would think ten servers, normally, would not go above 2000W (200W each), so your 3000 W backup should be enough.

[percentages]

>Will a 3000va UPS suffice?

Based upon the numbers you gave....Yes!

>I'm not looking for hours of UPS, just 5 or 10 minutes in the event there is a power flicker.

This sounds like a dangerous long term strategy to me.

What are you going to do if that "flicker" turns into a 2+ hour outage. Happens weekly here in Florida (during the summer months). Without a backup generator I wouldn't even think about running 1 server locally.

[ControlEngineer]

How can I judge the power draw from each machine

As defanjos suggest, a clamp meter should be used. Most electricians should be able to help you with this. With this much power use, you problably should have an electrician check over your wiring anyway. Be sure you cover the worst case. If fans turn on or off, the fans should be running when you check the power.

I'm not looking for hours of UPS, just 5 or 10 minutes in the event there is a power flicker.

So what happens if there is a 15 minute (or longer) outage? If your clients expect uptime, particularly for commerce sites, you should be expected to endure a long power outage. Get a generator with an auto start/transfer switch and size the UPS battery size for at least as much time for the generator to come on.

If there is a power failure, you can be sure it will be when no one is around to start the generator. You also want a small delay on the generator start so that it won't start for those 10 sec. flickers.

In my real job in industrial control we always protect the control system (even before they were all computerized) with UPS systems and backup generation. It is well worth it if you have clients who want their sites available all the time. (And know how many $/min it costs to be unavailable!).

[SEOMike]

So what happens if there is a 15 minute (or longer) outage?

I did mean short outages, but it would be a good idea to plan for a big one. As you all know, time IS money!

Thanks for the input. My search for a line meter and a generator starts now...