To beta or not to beta
that is the question. To anyone that then asks, "What do you mean create a partition?" my immediate response would be to NOT install beta software as your personal ability to recover from the negative experiences betas can provide is admittedly limited.
Beta software can run the gambit from no problems to a completely unusable system. One problem with betas is you never know what mix of hardware and software on any given system will provide critical mass that will cause that system to go nuclear. I've got Yosemite beta 5 running on a 2012 Mac Pro on a 1 TB external disk and have had no problems. However, that's a test system, and if it should go bump in the night I can re-boot to Mavericks, flush and format the external HDD, and start over. Would I put Yosemite on my laptop and use it in a critical environment? No, even given the stability I have seen.