A step-by-step account of how Disk Arbitration and APFS mount an external disk, from handling its partitions, to performing trims.
APFS
Update adds a 22nd tool, to display a log extract tailored to examining the mounting of APFS disks. Also valuable for any APFS investigation.
When you updated your iPhone or iPad to iOS 10.3 six years ago, you were among the first to use Apple File System, although you didn’t know it at the time.
Enabling the TRIM command was once thought important to maintain good write performance on SSDs. What has happened to it? Should we still be enabling it?
Traced from recognition of the cable connection, through establishing PCI streams, to mounting the volume with APFS, and the bonus of a good trim at the end.
Is the performance overhead of using APFS Encrypted volumes to store sensitive data a reason for not doing so?
You’re running bit short of disk space, so put tens of GB of old files into the Trash, then empty it. Why doesn’t the amount of free space increase?
Backing up with Time Machine to a NAS or other network storage is different. Here’s an account of how it creates and handles sparse bundle storage in Ventura 13.2.
How APFS can trim free space in a read/write disk image and transform it into a sparse file, so it uses storage more efficiently.
Plain read/write (UDRW), sparse image (UDSP), and sparse bundle (UDSB) compared for storage efficiency, performance, and convenience.
The Eclectic Light Company 