Unlike Windows-based computers, Macs usually do not come with multiple hard-drive partitions. It is just a single partition that you see when you first boot your Mac. Though there is no harm using your Mac with a single partition, it is highly recommended that you have at least two partitions on your machine. This will let you store your important files on one partition when the other one is being formatted. It is also helpful if you plan to install another OS beside your Mac OS. Regardless of your reasons, here’s how you can do it.
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How to Create a Partition on Your Mac (Make Tech Easier)