Together these volumes could require a maximum of around 40 GB at their peak. The System volume itself is just over 15 GB, and may require a bit more than that during updating.

The more recent Update volume is very small between updates, but is used for preparation and staging of macOS updates, when it could reach 15 GB or more. Preboot and Recovery are both relatively small, and should total well under 5 GB even during updating. Thus, to work out how much free space that container (and the whole disk) needs, you need to consider how much could be required for each of those volumes, and add them together to give a total. As they’re volumes within the same container, they share the same free space. There are now six volumes grouped together in the container from which your Mac boots macOS. Thankfully, those additional containers are small, well under 10 GB in total, so don’t need to be taken into account here. This is also different for the internal SSDs of M1 series Macs, which contain two additional hidden partitions/containers, which aren’t present in Intel Macs or external storage.

Since Catalina, macOS boot disks have had a formal structure which greatly affects free space. To keep this as simple as possible, I consider only disks which will be formatted in APFS, and are primarily used with Big Sur or Monterey. The simple answer is that it depends, and here I try to explain some of the more significant things it depends on. This has become one of the most popular questions put to me since the arrival of APFS, whether in specifying internal storage for a new Mac, or when managing external disks.

Minimum space for mac hi sierra