I've used a colocation service for about 3 months. This is my first touch to run web servers in a data center, so I don't have any idea and information about server hosting (or colocation).

Now, I'm running 15 1U servers in a full-rack because the data center has a payment policy depends on electricity usage. So there're a lot of empty slots in my rack, but I paid also space fee for the full-rack every month.

Is this case is common? I cannot use rest of space in the rack because of their 'common' hosting policy. They said that it's common and general rule in US, are they right? Please tell me the truth if you know anything about it. Thanks!



We have a similar issue in one of our data centers. Each one of our racks is provided redundant 20A power. This is roughly enough to hold, as you say, 15 1U servers (if they are low power consumption). In our region the best you can find is 30A per rack.

  • This is what I see in Australian DC's as well. 2kW/rack is standard here, and more gets expensive very quickly. Newer DC's are better. Remember that a few years ago 4ru cases were common, and used less power per host so this wasn't an issue. – LapTop006 Oct 25 '09 at 13:34

Yep, this is common. We originally were going to go with blade centers and consolidate into a single rack, but our Colocation facility charges double for L6 vs L5 circuits. Additionally, we couldn't get the power density, so we'd end up with 1 or 2 blade centers sitting in a mostly empty rack. This was the case at about 5 different facilities that I looked at. So, even though we would be using far less wattage, it would cost us more than twice as much.

So, we ended up with a bunch of 1U servers and redundant L5-30s in the cabinets, which is actually a good deal of power density from what we learned shopping around.


I've got two racks, one each in two colocations in different cities, and I've had two others in another colo before.

Generally speaking, you pay so much for a rack, and that rack comes with a certain amount of power. You can get more, but you've got to pay for it, because the colo only has a certain amount of power to give out.

If you look at their specs, they are rated in watts per square foot. This indicates not only how much power they have running to their building, but what their redundant power infrastructure is capable of. They have to provide generators to backup that much power, and they've also got to have battery banks to provide the gap between line power and generator startup. This is expensive, so making you pay for power is their way of recouping it.


It appears you are currently colocated in a facility with low power density. In a proper facility you would only be paying for half a rack and how much power you required. It isn't uncommon to see 60 amps over 110V in proper datacenters on a single rack, perhaps even 80A.

Keep in mind you cannot exceed 80% of your power allocation, due to fire safety standards.


Thank you everybody. Your all comments are very useful to me.

My servers are on a data center in California (nearby San Francisco). The datacenter guys told me we cannot exceed 80% of 20A power (per each rack) as gekkz said.

Yes, I've used 15 1U servers, but each of them is a power troll. It's really powerful, but eats a lot of power also. Then I've paid colo fee for over-half-empty rack.

Thank you again, and next time I'll check a server spec, especially power, carefully.

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