Using Y split cables to connect two servers to a single PDU receptacle

We have bought a few 30amp 208v PDUs that only have 9 receptacles. The servers we are connecting to those PDUs will not use the full 30amps (at 80%, or actually 40% since we use redundant power) so we need to find a way to connect more than 9 servers to the same 9 receptacles so we'll be not wasting capacity that we pay for.

I thought about using a Y split cable like this one: http://www.cablesandkits.com/power-cord-c14-c13-splitter-cable-awg-p-515.html

That will let me connect two servers to a single receptacle.

Each of the individual receptacles can provide 12 amps of power and individual servers are unlikely to consume more than 3 amps at maximal load so it should provide sufficient power.

The question is if there is any other reason why this may be a bad idea and if there is any other solution other than buying PDUs with more receptacles (which I don't want to do because I must use horizontal PDU on these racks and ones with more receptacles consume more U space).

In general, the problems you encounter with these are much the same as you do with double adapters and power boards in your home. Some problems you'll possibly encounter:

• Doing power maintenance can get "interesting";
• Routing the cables is more fiddly and hard to get neat;
• Governmental or facility regulations may prohibit the use of such things on safety grounds;
• Managed power rails (remote switched or metered) lose quite a bit of their utility.

For myself, I wouldn't use 'em ever again, but that's largely because the company I work for sees the benefit in forking out the extra money on two or four 0RU remote-switched power rails for everything, so having power ports available is rarely, if ever, a problem. These days, having enough amps available is more of a concern than physical space in the environments I work in.