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.
Storage Management
What happens when a Mac runs out of free space in the container of its boot volume group? This shows what you can expect to see, and what happens in the log.
You’re running out of free space, so check in Storage settings to see where it has all gone. System Data has reached 50 GB, but what is that, and what should you do to reduce it?
Among the most useful are Archive Utility, now including Apple Archive compression, and Storage Management. But Network Utility is now non-functional.
Sierra sticks with the old favourites like Disk Utility, but still can’t repair permissions or keychains. A new app, Storage Management, has been added.
