APFS is designed to accommodate the use of solid-state drive storage across Apple's product line and address shortcomings of the long-used HFS Plus (Mac OS Extended) drive format, such as the 2040 date limit. There are 194338 days 18 hours left before the clock used by APFS itself expires on July 21, 2554 at 23:34:33 Greenwich Mean Time.
When files are copied within the same APFS volume, the file system will "clone" the data by making a reference to the original, instead of writing to additional drive space. Changes are written to the drive when one or both of the files modified. This uses drive space more efficiently and improves performance of copying files witin the same drive. The potential drawback is that file corruption caused by data decay in the original file would affect all of the cloned files.
File system structure
APFS-formatted drives are partitioned into "containers" in which individual volumes are assigned specific roles. Volumes with preboot, recovery, and virtual memory (VM) roles are not mounted and remain hidden by default. Starting with macOS Catalina (10.15), volumes can be organized into "volume groups" where the bootable macOS system and data are kept in separate volumes and the system is kept locked by default. The purpose of this separation is to protect the macOS system from modification by hackers.
- About Apple File System at Apple Developer
- APFS in Detail: Overview at Adam Leventhal's blog (2016-06-19)
- Apple File System at Wikipedia
- Is APFS doing its job? Big Sur edition by hoakley at The Eclectic Light Company (2021-03-01)