The size of operating systems is growing, as is the size of internal storage. Luckily, the latter has grown faster and now it is possible to run two, or more, different versions of OS X, side-by-side, on the same internal hard drive. And there are good reasons for doing this.
In this tutorial, I will show you how to partition and prepare your Mac’s internal hard drive such that you can boot the machine into your choice of a number of versions of OS X.