In hardware encryption, keys are kept in the Secure Enclave. Software encryption in APFS has no such luxury, just keybags at container and volume level. This explains when they’re created.
APFS
macOS 27 has changed log entries that confirm that an SSD is being trimmed correctly when it’s mounted. Full details explain how you can verify Trimming.
In APFS, containers, volumes and folders have different properties and features. Choosing the right one, and setting any size options, is an important step in good storage management.
Caching to disk improves performance, but cached data are optional and may be purged when additional free space is needed. This explains how that’s performed by the deleted service.
Further tests on two volumes with over 90 GB purgeable space. One took almost 30 minuted to become available, the other never got there at all. The log reveals who was responsible.
Snapshots made by Time Machine and tmutil should be purgeable, although sometimes they won’t purge, and aren’t shown reliably as purgeable space. An exploration of bugs and missing documentation.
All APFS volumes in a single partition/container share its free space. How can that be measured? How much could be purged, and how do special file types affect it?
To work out how long you’ll be able to use your present backup storage, you need to know how much space is free now, and the rate at which free space is being used by further backups. This app can forecast that, and more.
How to resolve an inode number to a path and filename, and how to go the other way from a file to an inode number. How you can tell which files are on System and Data volumes.
Trimming ensures an SSD can write data as fast as it can read it. Although most SSDs should be Trimmed when they’re mounted, if you’re unsure, here’s simple test to tell whether any SSD does Trim correctly.
