Apple File System

Apple File System
Developer(s) Apple Inc.
Full name Apple File System
Introduced March 27, 2017 with iOS 10.3
Limits
Max. file size 8 EiB
Max. number of files 263
Features
Date resolution Nanosecond
Transparent encryption Yes
Copy-on-write Yes
Other
Supported operating systems macOS, iOS, tvOS, and watchOS

Apple File System (APFS) is a proprietary file system for macOS, iOS, tvOS and watchOS,[1] developed and deployed by Apple Inc.[2][3] It aims to fix core problems of HFS+ (also called Mac OS Extended), APFS's predecessor on these operating systems. Apple File System is optimized for flash and solid-state drive storage, with a primary focus on encryption.[4][5]

History

Apple File System was announced at Apple's developers conference (WWDC) in June 2016 as an upcoming replacement for HFS+, which had been in use since 1998.[4][5] It was released for iOS devices on March 27, 2017, with the release of iOS 10.3.[6][1] It is being released for macOS devices beginning with macOS 10.13, released in beta on June 5, 2017, and coming for general release in the fall.

Design

The file system scales from an Apple Watch to a Mac Pro. It uses 64-bit inode numbers, and allows for more secure storage. The APFS code, like the HFS+ code, uses the TRIM command, for better space management and performance. It may increase read-write speeds on iOS and macOS,[1] as well as space on iOS devices, due to the way APFS calculates available data.[7]

Clones

Clones allow the operating system to make efficient file copies on the same volume without occupying additional storage space. Changes to a cloned file are saved as deltas, reducing storage space required for document revisions and copies.[3]

Snapshots

Apple File System supports snapshots for creating a point-in-time, read-only instance of the file system.[3]

Encryption

Apple File System natively supports full disk encryption, and file encryption with the following options:

Increased maximum number of files

APFS supports 64-bit inode numbers, supporting over 9 quintillion files on a single volume.[8]

Data integrity

Apple File System uses checksums to ensure data integrity for metadata, but not user data.[9]

Crash protection

Apple File System is designed to avoid metadata corruption caused by system crashes. Instead of overwriting existing metadata records in place, it writes entirely new records, points to the new ones and then releases the old ones. This avoids corrupted records containing partial old and partial new data caused by a crash that occurs during an update. It also avoids having to write the change twice, as happens with an HFS+ journaled file system, where changes are written first to the journal and then to the catalog file.[9]

Space Sharing

APFS adds the ability to have multiple logical drives (referred to as Volumes) in the same container where free space is available to all volumes in that container.[10] An APFS container can be either a single physical partition or built from two partitions on separate drives such as a Fusion Drive.

Limitations

In its first generation, Apple File System does not provide checksums for user data, but does for metadata integrity.[11] It also does not take advantage of byte-addressable non-volatile random-access memory,[12] and does not support compression yet.

Currently released versions of Apple File System do not perform Unicode normalization while HFS+ does,[13] leading to problems with languages other than English.[14] The version in beta releases of macOS High Sierra does perform normalization.[15]

Support

macOS

Apple File System is available in macOS Sierra, albeit with numerous limitations; it is considered experimental. Among its limitations:[16]

A drive partition can be formatted with APFS in macOS Sierra with the diskutil command-line utility. APFS will be used as the default file system for macOS beginning with macOS High Sierra.

iOS, tvOS, and watchOS

iOS 10.3, tvOS 10.2, and watchOS 3.2, released on March 27, 2017, convert the existing HFS+ file system to APFS on compatible devices.[6][1][17]

See also

References

  1. 1 2 3 4 Warren, Tom (March 27, 2017). "Apple is upgrading millions of iOS devices to a new modern file system today". The Verge. Vox Media. Archived from the original on March 27, 2017. Retrieved March 27, 2017.
  2. ↑ Roger Fingas (June 13, 2016). "'Apple File System' will scale from Apple Watch to Macs, replace HFS+". Apple Insider. Archived from the original on July 23, 2016.
  3. 1 2 3 4 Hutchinson, Lee (June 13, 2016). "Digging into APFS, Apple's new file system". Ars Technica UK. Retrieved June 15, 2016.
  4. 1 2 Weintraub, Seth (June 13, 2016). "Apple File System (APFS) announced for 2017, scales ‘from Apple Watch to Mac Pro’ and focuses on encryption". 9to5Mac. Archived from the original on March 28, 2017. Retrieved March 27, 2017.
  5. 1 2 Hutchinson, Lee (June 13, 2016). "New file system spotted in macOS Sierra [Updated]". Ars Technica. Condé Nast. Archived from the original on March 28, 2017. Retrieved March 27, 2017.
  6. 1 2 Clover, Juli (March 27, 2017). "Apple Releases iOS 10.3 With Find My AirPods, APFS, App Store Review Tweaks and More". MacRumors. Archived from the original on March 27, 2017. Retrieved March 27, 2017.
  7. ↑ Alan Loughnane. "Updating your iPhone will give you one major benefit". joe.co.uk. Archived from the original on May 20, 2017.
  8. ↑ Apple Inc. "Apple File System Guide (Features)". Retrieved July 1, 2017.
  9. 1 2 Adam Leventhal (June 19, 2016). "APFS in Detail: Data Integrity". Archived from the original on June 21, 2016.
  10. ↑ "Archived copy" (PDF). Archived (PDF) from the original on October 23, 2016. Retrieved June 10, 2017.
  11. ↑ A ZFS developer’s analysis of the good and bad in Apple’s new APFS file system Archived February 2, 2017, at the Wayback Machine.
  12. ↑ Why Apple's APFS won't last 30 years Archived April 6, 2017, at the Wayback Machine.
  13. ↑ APFS’s “Bag of Bytes” Filenames
  14. ↑ APFS is currently unusable with most non-English languages – The Eclectic Light Company Archived June 8, 2017, at the Wayback Machine.
  15. ↑ What's new in Apple File System
  16. ↑ "How to Format a Drive With the APFS File System on macOS Sierra". Archived from the original on October 26, 2016. Retrieved October 26, 2016.
  17. ↑ "jakepetroules/Filesystem". GitHub. Retrieved March 29, 2017.
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