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.
APFS
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.
Support for encrypted HFS+ ends next year in macOS 28. Does that also affect encrypted disk images? Could you use in situ conversion to APFS Encrypted on old Time Machine backups?
When you First Aid in Disk Utility, or an equivalent command tool, it reports the formatting and modification details of each volume. Here’s how to interpret them, with details of all versions of APFS and when they were released.
Have you got any encrypted HFS+ disks you still back up to, or tucked away in storage? Now is the time to plan what to do with them. Here is a guide with practical suggestions.
Apple has announced that support for HFS+ encryption will be removed in a future version of macOS. How this is all about ending support for CoreStorage, and where it has gone since then.
The Eclectic Light Company 