As Time Machine has changed, first to back up APFS volumes, then to create backups as snapshots, its needs have changed. This makes it complicated to decide which local snapshots you can delete without affecting its backups.
APFS
Fundamentally simple: a preserved copy of a volume at a moment in time. How its size can only increase with time, how they’re managed, what they’re used for, and the tools for using them.
It makes a big difference whether an app, file or folder is in the System or Data volume, or maybe somewhere else. Here’s how to tell accurately, rather than according to one of the Finder’s illusions.
How to read a UUID to determine whether it’s supposed to be random, or has a specific meaning. Where you’ll find them, and whether you’ll ever see two the same.
Add another volume to your Mac’s internal SSD and try to eject it. All hell breaks loose as the Finder wants to eject the whole disk, it seems. Probably a 6-year old bug.
A survey of support for APFS, HFS+, FAT and ExFAT, NTFS, ZFS, Linux file systems, and MacFUSE with its potential for file systems running in user-space.
Trim enables an SSD to erase pages of unused memory so they’re ready for reuse. It saves time, and greatly improves write performance. How to the best out of Trim.
Study how the four key timestamps of a file change when you create, edit, preview the file, using Dropera.
Two confounding factors to take into account when interpreting timestamps on files: what updates the Last opened time, and access via QuickLook.
First Aid in Disk Utility, or fsck_apfs in Terminal, have given warnings or errors with id numbers. How do you work out which file or folder that refers to?
The Eclectic Light Company 