As far as I'm concerned, I find the following network architecture to be pretty good/common practice:

• 1 public IP per physical site (more if you want backup lines)
  
• VPN between all the physical sites (to interconnect offices)
  
• 1 internal network per "service" (development, testing, benching, ...)
  

This architecture is easy to maintain and understand. The hardest part here is to figure out the mask for each internal network.

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For electrical/cooling system, I must say I'm no expert. All I know is that our server room has its own electrical circuit that's independent within the building, and we have 3 air conditionners in the room to keep it at around 20°C.

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For OS deployment, well, it depends on the purpose of the machine. We actually install the OS by hand every time, be it a windows computer, centos server, or esxi, or whatever we need.
For most linux server, we then use a configuration management system to "bootstrap" the machine and give it a purpose.

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Regarding storage, you don't have much more choice than buying some here and there, or rely on an outsite service that will handle that for you.
I personally (like, at home) use 3 backup methods:

For my desktop, everything is both on my acutal drive, on a second harddrive INSIDE the computer, and on a usb drive sitting on my desk. It means that if my house burns, I'll loose my data...
The problem is that for the amount of data I have, online backup solution are too expensive... My plan was to buy cheap boxes to get running in house of people I know, or build a "circle of trust" with people online to backup my things in multiple places.
I'm still "working" on that part...

For servers, I use tarsnap to backup my server's configuration and data. The service is pretty cheap, and I trust the guy.
My main server (the one with the most diskspace) fetches data via rsync from its peers over a VPN to a local folder, then weekly send the data to tarsnap server.
I then get a report of the uploaded data in my mail, as a reminder that my backup is working.

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That's all folks!