When the numbers simply don’t add up. How some extended attributes may be included in quoted file sizes, but others are ignored, and Sequoia hasn’t really changed this since Classic Mac OS of 25 years ago.
HFS+
A brief start with MFS for 400 KB floppies, followed by HFS intended for the first hard disks, upgraded to HFS+ in 1988, and followed in 2017 by APFS for all the OSes.
How read-write disk images and those used in Apple silicon virtual machines use sparse file format to save space on disk.
Deciding which file system to use for hard disks can be difficult. Here are the advantages and disadvantages explained in detail, for HFS+ and APFS.
First securing the Home folder in an encrypted sparse disk image, then to whole-volume encryption using CoreStorage, now using T2 and Apple silicon chips.
When do sparse files explode to full size, and how could you preserve them in transit? Can you copy clones or snapshots? How to preserve extended attributes?
APFS or HFS+? Which can Time Machine back up to? What about hard disks? Which format for use on PCs? And which are supported by Disk Utility now?
macOS has an elaborate set of rules determining which types of xattr are preserve during different types of copying, including syncing to iCloud Drive. Here they are in full detail.
Extended attributes were added to Mac OS X 10.4, and soon supported the quarantine xattr. They have since flourished, and have valuable properties.
Released in Mac OS X 10.5 Leopard on 26 October 2007, it supported Time Capsules launched in January 2008, and in Big Sur could back up to APFS.
The Eclectic Light Company 