macOS supports several different disk formats, each of which has its purposes. This article explains which to choose from those you can create by form

Which disk format?

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2024-09-28 14:30:05

macOS supports several different disk formats, each of which has its purposes. This article explains which to choose from those you can create by formatting a disk in Sequoia. macOS also supports some other formats like NTFS for reading only, which I won’t cover here.

Before any file system can be formatted on a disk, the storage in the disk must be partitioned using one of three standard schemes:

Even if the whole of the disk is going have just one file system or volume, one of those is required, as it stores information about how the space on the disk is allocated.

Apart from APFS, most file systems you’re likely to use require a whole partition on the disk for each volume. For example, an HFS+ disk with two volumes is divided into two partitions, each of which contains one HFS+ volume. Because partitioning is intended to be static, that means those two volumes have fixed size, and don’t share free space between them. Once created, it’s possible to change partitioning, and Disk Utility will try to do so non-destructively, without losing any data in the volumes, but that isn’t always possible.

APFS volumes are different, and share free space within a partition, termed a container in APFS terminology. APFS containers are essentially similar to HFS+ volumes, as they’re static partitions, but APFS volumes are sized dynamically within their static container.