Neha Patil (Editor)

Apple File System

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Developer(s)
  
Apple Inc.

Max. file size
  
2 bytes

Date resolution
  
Nanosecond

Full name
  
Apple File System

Max. number of files
  
2

Transparent encryption
  
Yes

Apple File System (APFS) is a file system for macOS, iOS, tvOS and watchOS, currently being developed and deployed by Apple Inc. It aims at addressing the core issues of the existing HFS+ file system in use on these platforms today.

Contents

Overview

Apple File System is optimized for flash and solid-state drive storage and features a copy-on-write design that uses I/O coalescing for improved performance. It was designed to scale from Apple Watch to Mac Pro.

Clones

Clones allow the OS to make fast, power-efficient file copies on the same volume without occupying additional storage space. Modifications to the data write the new data elsewhere and continue to share the unmodified blocks. Changes to a file are saved as differences of the cloned file, reducing storage space required for document revisions and copies.

Snapshots

Apple File System supports snapshots for creating a point-in-time, read-only instance of the file system.

Encryption

Apple File System will implement disk encryption for files and sensitive metadata. It will support the following encryption models for each volume in a container:

  • no encryption,
  • single-key encryption, and
  • multi-key encryption, which encrypts each file with a separate key, with metadata encrypted with another one.

    • Data integrity

    Apple File System uses checksums to ensure data integrity for metadata, but not user data.

    Crash protected

    Apple File System is designed to be crash protected.

    Limitations

    Apple File System does not provide checksum for user data, but it does checksum metadata for integrity. Additionally, it does not take advantage of byte-addressable non-volatile random-access memory.

    macOS

    Apple File System is available — but with numerous limitations — in macOS Sierra, and is considered experimental. Among the limitations:

  • Drives formatted with Sierra’s version of APFS may not be compatible with future versions of macOS nor the final version of APFS.
  • There is currently no supported way to convert an HFS+ volume to APFS.
  • The only option currently available for APFS is a case sensitive filesystem.
  • APFS cannot be used with Time Machine, FileVault encryption, or Fusion drives.

    • A drive partition can be formatted with APFS in macOS Sierra with the diskutil command-line utility. A final version is expected in 2017.

    iOS

    iOS 10.3 will convert the existing HFS+ file system to APFS on devices compatible with iOS 10.

    References

    Apple File System Wikipedia
    (Text) CC BY-SA


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