Need advice on best UPS / Redundant Power Supply Setup

[mightybs]

I am currently adding another UPS system into my workplace server room, and I wanted to evaluate the way the current setup is, so that I can determine whether or not I should take time to redesign the setup. So I'm looking for recommendations on how others have setup servers with redundant power supplies and UPS units.

For instance: With redundant supplies, where do you have them plugged in? 1 to a UPS? 1 to the wall? Same or separate circuits?

Should I only have one power supply in a UPS, or should there be more?

We do have a generator for our building, and soon will have a separate one just for the server room, so the UPS on needs to carry the machines for 30 secs or so, and so far they have been doing their job, I just wanted to know again about people's "best practices" setups.

 

[PSWired]

Here's how I have my servers set up:

Each server has one UPS per power supply. The main fileserver has two power supplies, each one has its own separate UPS. Each one of these UPSes is plugged into a different circuit, and the circuits are on different phase legs of the building's electrical system. This way if one phase is taken out (tree falling on wire) the server will continue to operate. Also a single UPS failure will not cause the server to fail.

Each UPS is sized to provide the desired runtime for the server based on its power consumption.