Apple File System (APFS) is a proprietary file system for macOS, iOS, tvOS and watchOS, developed and deployed by Apple Inc. 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.
Video Apple File System
History
Apple File System was announced at Apple's developers conference (WWDC) in June 2016 as a replacement for HFS+, which had been in use since 1998. It was released for iOS devices on March 27, 2017, with the release of iOS 10.3, and for macOS devices on September 25, 2017, with the release of macOS 10.13.
Maps Apple File System
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, as well as space on iOS devices, due to the way APFS calculates available data.
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.
Snapshots
Apple File System supports snapshots for creating a point-in-time, read-only instance of the file system.
Encryption
Apple File System natively supports full disk encryption, and file encryption with the following options:
- no encryption
- single-key encryption
- multi-key encryption, where each file is encrypted with a separate key, and metadata is encrypted with a different key.
Increased maximum number of files
APFS supports 64-bit inode numbers, supporting over 9 quintillion files on a single volume.
Data integrity
Apple File System uses checksums to ensure data integrity for metadata, but not user data.
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.
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.
Limitations
In its first generation, Apple File System does not provide checksums for user data, but does for metadata integrity. It also does not take advantage of byte-addressable non-volatile random-access memory, and does not support compression yet.
Unlike versions of HFS+ since Leopard, APFS has no support for hard links to directories. This is in line with many other modern file systems, but Time Machine still relies on them, so APFS is not yet an option for its backup volumes (as of macOS 10.13 High Sierra).
Support
macOS
macOS High Sierra automatically converts the file system on devices with all flash storage to APFS. FileVault volumes are also converted, but Fusion Drives and hard disk drives are not. Users cannot opt out of this conversion, and devices formatted with the High Sierra version of APFS will not be readable in previous versions of macOS.
An experimental version of APFS, with some limitations, is available in the previous version of macOS (Sierra) through the command line diskutil utility. Among these limitations, it does not perform Unicode normalization while HFS+ does, leading to problems with languages other than English. Drives formatted with Sierra's version of APFS may also not be compatible with future versions of macOS or the final version of APFS, and the Sierra version of APFS cannot be used with Time Machine, FileVault volumes, or Fusion Drives.
iOS, tvOS, and watchOS
iOS 10.3, tvOS 10.2, and watchOS 3.2 convert the existing HFSX file system to APFS on compatible devices.
See also
- Comparison of file systems
- Btrfs
- HAMMER
- ReFS
- Write Anywhere File Layout
- ZFS
References
External links
- Apple File System Guide at Apple Developer
- APFS in Detail: Overview
Source of article : Wikipedia
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