I am running OSX 8.5 "Mountain Lion" on a Basic Mac Mini i5(Late 2012), 16GB RAM and 500GB HD which is problem free. I want to upgrade some important Apps like Pages, Keynote, etc. but cannot do this until I upgrade to "Yosemite". I am seriously thinking of purchasing either a 120GB or 240GB "OWC Mercury Elite Pro Mini Portable" SSD External Drive BEFORE I do this upgrade to "Yosemite"; Reason: HD Drive could be a serious bottleneck after I upgrade the OS. Your suggestions will be truly appreciated.