February 2022 • Macworld 17

W

ith macOS Catalina,

Apple changed

macOS’s structure

on a start-up volume.

Instead of a single commingled set

of system and data files, with Apple

trying to ensure the integrity and

Choosing this option ensures both your system and data volumes are

deleted. Glenn Fleishman reports

How to erase a Mac’s

hard drive

immutability of system files, the

company split it into two parts: a

system volume and a Data volume.

The two are melded together into

a ‘volume group’, an organizational

method added in Catalina. When you

boot macOS Catalina or later, the