"According to Apple, APFS supports all of HFS+ features and improves them in several ways:
- Contrary to HFS+, which uses 32-bit file IDs, APFS will support 64-bit inode numbers, which will allow to store over 9 quintillion files on a single volume.
- Whereas HFS+ is bound to initialize the entire storage of a file system at once, APFS sports an extensible block allocator that enables lazy initialization of its data structure, thus hugely improving performance with large volumes.
- APFS supports three models of encryption: no encryption, single-key encryption, and multi-key encryption to manage per-file keys and a metadata key.
APFS also provides a few advanced features that put it in the same category as modern file systems such as ZFS,"
Introduction @ Apple
"Apple File System is a new, modern file system for iOS, OS X, tvOS and watchOS. It is optimized for Flash/SSD storage and features strong encryption, copy-on-write metadata, space sharing, cloning for files and directories, snapshots, fast directory sizing, atomic safe-save primitives, and improved file system fundamentals."