Apple File System to Replace Old HFS+ in 2017

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.

Important: APFS is released as a Developer Preview in OS X 10.12, and is scheduled to ship in 2017.

Apple File System Adds Several New Features
Apple File System provides several new features, including optimization for flash/SSD storage, copy-on-write metadata, space sharing, cloning of files and directories, snapshots, fast directory sizing, and atomic safe-save primitives.

Flash/SSD Optimization
APFS is optimized for flash/SSD storage and can be used with traditional hard disk drives HDD. A unique copy-on-write design uses I/O coalescing to maximize performance while ensuring data reliability.

Space Sharing
Space Sharing allows multiple file systems to share the same underlying free space on a physical volume. Unlike rigid partitioning schemes, which pre-allocate a fixed amount of space for each file system, APFS volumes can grow and shrink without volume repartitioning.

Each volume in an APFS container reports the same available disk space, which is equal to the total available disk space of the container. For example, for an APFS container with a capacity of 100GB that contains volume A, which uses 10GB, and volume B, which uses 20GB, the free space reported for both volumes A and B is 70GB (100GB – 10GB – 20GB).

Cloning of Files and Directories
A clone is a nearly instantaneous copy of a file or directory that occupies no additional space for file data. When a cloned file is modified, only the modified blocks are written to new locations on storage. In this way, the file system can store multiple revisions of the same document with less storage space.