* V, then A = W / V. So, 460 watts divided by 120 volts = 3.83 amps. Five servers using 3.83 amps each will require a total of 19.15 amps. Of course, this assumes a full load on the electrical circuits. Many collocation facilities will not allow you to load your circuits over a set threshold (typically, 70 Chapter 33: Designing Networks percent). If we can only load our circuits to 70 percent, we can only put three or maybe four servers on each PDU. Thus, even though we only have 12 servers, if each PDU is only capable of 20 amps, we'll still need four PDUs. Because we can only fit 12 servers in a rack (assuming four PDUs), it makes sense to space them out. Working on 1-RU servers can be difficult with all the connections they may have. As you'll see, having six Ethernet interfaces in each server is not unusual. Don't forget that each server will also have console cables, power, and the wire management necessary to support it all. Additionally, if you leave a large empty space in the rack, executives will expect you to fill it before they allow you to order additional racks. Tips for Network Diagrams Engineers seem to like to make their documents SO complicated that even they have trouble reading them. Here are some tips to help you produce documentation that will get you noticed: Keep it simple Take a look at any of the drawings in this book. Each one of them is designed to convey a single idea. The more you try to include in a drawing, the harder it will be to understand. Separate physical and logical ideas Physical connectivity is very important, but try to keep it separate from VLANs, routing, and other logical subjects. I like to make two drawings: one for the physical ports, and another with the VLANs and IP addresses. With the use of SVIs, this becomes even more important. Don't cross lines Every time you cross a line in a drawing, the drawing gets harder to read. Some- times, it's unavoidable, but try to keep crossed lines to a minimum. Orient your straight lines If you put together a drawing in which the