I have been starting up my iMac (Mavericks) with a flash drive that boots up Mountain Lion so that I can use an app that is incompatible with Mavericks. Question: I have a single external backup drive always connected to my Mac. I am thinking of partitioning that drive and giving each partition a unique name, e.g., Backup 1 and Backup 2. I intend then to boot up in Mavericks and tell Time Machine to back up to Backup 1, and then boot up in Mountain Lion and tell Time Machine to back up to Backup 2. Will this work, i.e., will the appropriate partition automatically back up the system in which it is booted?