Plain read/write (UDRW), sparse image (UDSP), and sparse bundle (UDSB) compared for storage efficiency, performance, and convenience.
Disk Utility
All you need to know about the sparse RAW disk images used inside lightweight VMs on Apple silicon Macs.
In Monterey and Ventura, regular read-write UDRW disk images can now be APFS sparse files, and work more efficiently than sparse images or sparse bundles.
Disk images originated in the 1960s, and are still valuable tools in modern macOS. They have their limitations, though, and in some cases should be replaced by APFS volumes.
You’re in control of a traditional file system, but with snapshots, clones, sparse files and other volumes sharing free space, APFS isn’t as simple.
Once, you could run diskutil to ‘fix’ broken permissions in your Home folder, then it was replaced by repairHomePermissions in Recovery. Apple no longer documents this, but it’s still there. Should you use it?
Has Ventura brought any relief from Disk Utility’s inability to run First Aid on Time Machine’s backups, and what about changes in Time Machine itself?
A simple worked example showing the effect of snapshots and changes in hidden system files in consuming free space on APFS.
They have more options than most new cars. What are they, how do you use them, how to pick the most appropriate, and which tools to use.
Apple could have chosen to make APFS open source or to document it fully, to help third parties develop maintenance tools. It chose not to, but Disk Utility still doesn’t work as it should.
The Eclectic Light Company 