What is the minimum partition size for Mac OS 10.10 Yosemite? I'm about to set up a Mac mini to dual boot Mavericks and Yosemite for software development purposes. What's the recommended minimum size of a Yosemite partition?
I have run Mavericks/Yosemite on a 64 GB SD card and after a clean install, there was about 20-30 GB free.

I would say that you could install Yosemite on a 20 GB partition, but I would not recommend anything less than 30 GB.