In HFS+, a disk consists of one of more fixed-size volumes, which were often referred to as partitions. Once you have got past the confusing terms and tripwires in Disk Utility, this should prove fairly simple to set up.īefore we get started, it’s important to synchronise terminology, particularly if you’re still more used to using the old Mac Extended file system, HFS+.

Sometimes having an external drive that can boot one version of macOS isn’t enough: you want it to boot two (or even more).