Dual rackmountable power supply?

Do any of you know if there are companies who manufacture 1/2U
rackmountable PDU's that take AC from redundant sources? I have
equipment at a colo that seems to have issues with one of the two
circuits in my cabinets about once a month. Since it would be a
real pain in the neck for me to retrofit every server with dual-ps,
I was thinking this could be a possible middle-of-the-road solution.

Have a look at APC (http://www.apcc.com/products/family/index.cfm?id=14&ISOCountryCode=us)


Without 1-1 transformer and complex switching circuitry you really can't do safe switching from one to the other. That pretty much means any such device would be just as complex or more so as UPS, but less safe. So I think your best bet is to decide if your power problems last long and if they dont last more then several minutes and then just use regular UPS or if its bigger problem, then use UPS that can accept redundant power sources.

For servers with redundant power supply its quite different because they do provide power to the board from multiple sources and each one is already DC so its not a problem to switch quickly then.

This is called a "Static Transfer Switch". (Sometimes "automatic transfer
switch", particularly for smaller units). Number of companies make small