What Is APFS (Apple File System)? | phoenixNAP IT Glossary

APFS, or Apple File System, is a modern file system developed by Apple Inc. It's designed to optimize performance on solid-state drives (SSDs) and provide robust features like strong encryption, space sharing, and crash-safe protections.

What Is APFS?

APFS, or Apple File System, is the file system developed by Apple Inc. specifically for its operating systems, macOS and iOS. It was introduced in 2017 with macOS High Sierra and is optimized for flash and solid-state drive storage, with a focus on encryption, reliability, and performance. Developed to replace the aging Hierarchical File System Plus (HFS+), APFS is engineered to maximize the performance and reliability of modern storage technologies.

APFS offers several notable features including improved data integrity, space optimization through cloning and snapshots, strong native encryption for better security, and efficient metadata handling for quicker access and space management. Additionally, it supports crash protection to maintain consistency and prevent data loss in the event of system failures. APFS is now the standard file system across all Apple products, including macOS, iOS, watchOS, and tvOS.

A Short History of APFS

APFS was first announced at Apple's Worldwide Developers Conference (WWDC) in June 2016. At this stage, it was introduced as a modern file system designed to replace the aging HFS+, which had been in use since 1998. The primary design goals of APFS were to optimize for flash/SSD storage, which was becoming standard across Apple's product line, and to incorporate advanced features such as strong encryption, space sharing, and robust crash protection.

In 2017, with the release of iOS 10.3, APFS was rolled out to all iOS devices through an update process that seamlessly converted the existing HFS+ system to APFS. This deployment was a crucial test of APFS's capabilities and stability, particularly given the vast number of devices and the variety of data involved. Later in 2017, macOS High Sierra was released, bringing APFS to Mac computers. The upgrade to APFS was automatic for SSDs, while Fusion Drives and traditional hard drives initially retained the HFS+ format before also transitioning to APFS at a later date.

Since its initial releases on iOS and macOS, APFS has continued to evolve. It has been optimized further for efficiency and speed, and Apple has extended its use to all new installations of macOS, iOS, watchOS, and tvOS. Today, APFS is the default file system across all of Apple's product lines.

APFS Features

APFS represents a significant technical evolution aimed at better handling the demands of Apple's modern devices. Here are some key features of APFS:

Optimized for SSDs. APFS is designed to operate with the low-latency characteristics of solid-state drives, offering improved read/write speeds and better space allocation.
Space sharing. It allows multiple file systems to share the same underlying free storage space on a physical volume. This is useful in multi-boot configurations and for managing storage across different users or applications without needing to partition the drive.
Cloning of files and directories. APFS can create copies of files and directories without duplicating the data on the disk. The process is instantaneous and saves disk space.
Snapshot and versioning. It supports snapshots and versioning, which allows the system to capture and save the state of a file system at a particular point in time. This feature is helpful for backup and recovery processes.
Strong encryption. APFS provides strong encryption options with support for both single-key and multi-key encryption, which can encrypt files, metadata, and even individual directories separately.
Crash protection. APFS enhances data integrity and minimizes the risk of corruption through its crash protection features, which ensure operational consistency even in the event of system failures.

APFS Formats

Apple File System (APFS) supports several formats, each designed to cater to different types of storage devices and specific use cases. Here's a list of the key APFS formats:

APFS (case-sensitive). This format treats file names that differ only in letter case as distinct (e.g., "File.txt" and "file.txt" would be considered two separate files). It's useful for developers or in situations where case sensitivity is required for compatibility with UNIX-like systems.
APFS (case-insensitive). The default format for most users, this version of APFS treats file names that differ only in letter case as the same (e.g., "File.txt" and "file.txt" would be considered the same file). This is suitable for general use and is the standard format for macOS installations.
APFS (encrypted). This format provides strong encryption at the file system level, offering enhanced data security. It can be either case-sensitive or case-insensitive, based on user preference.
APFS (case-sensitive, encrypted). Combines case sensitivity with encryption, providing both specific file naming requirements and security features.

APFS Advantages and Disadvantages

Users should consider the type of operations they want to perform before committing to APFS, as the system presents a particular set of benefits and downsides. Here are the pros and cons of using APFS:

Advantages

APFS (Apple File System) offers several advantages over its predecessor, HFS+, and other traditional file systems. Here's a list of APFS key benefits:

Optimized for SSDs. APFS is designed specifically for solid-state drives (SSDs) and other flash storage technologies, which are standard in most modern Apple devices. This optimization results in faster read and write speeds and more efficient space allocation.
Space efficiency. APFS includes features like cloning and snapshots, which allow it to manage space more efficiently. Cloning files and directories does not duplicate the actual data unless modifications are made, saving valuable storage space. Snapshots provide a way to capture the file system at a specific point without needing to duplicate the entire file system's contents.
Strong encryption. APFS provides robust encryption options, supporting both single-key and multi-key encryption to secure file data and metadata. This feature enhances user data security, which is particularly important in an era where data breaches are common.
Crash protection. APFS enhances data integrity with its crash protection features. It uses a copy-on-write mechanism that ensures that data is not overwritten directly. Instead, new writes are committed to disk only after they're completely written, which helps preserve the integrity of the data in the event of a crash.
Snapshot and versioning. APFS supports creating snapshots of the file system, which can be used to back up and view older versions of files.
Space sharing. APFS allows multiple file systems to share the same storage space. This can be particularly useful in a multi-user environment or where multiple partitions are needed, as it avoids the need to pre-allocate fixed amounts of storage to each partition.
Fast directory sizing. APFS can quickly calculate the size of a directory and its contents, which improves the performance of tasks that require such calculations.
Unicode support for filenames. APFS supports Unicode for file names, which provides a greater range of characters and symbols in filenames, making it more flexible in a globalized environment.
Improved time stamping. APFS offers nanosecond timestamp granularity, which is an improvement over the second-level time stamps in HFS+. This allows for more precise modification tracking and is beneficial in environments where files are frequently updated.

Disadvantages

While Apple File System (APFS) offers numerous advantages tailored for modern storage technologies and Apple devices, it also has some limitations that are important to consider:

Compatibility issues. APFS is designed specifically for Apple's ecosystem. This can pose challenges when trying to share drives or data with systems running other operating systems, like Windows or Linux, which may require third-party software to properly read APFS-formatted drives. Devices running older versions of macOS prior to High Sierra cannot natively read or write to APFS-formatted volumes, which can complicate data transfer and backward compatibility.
Data recovery complexity. Due to its new and complex structure, data recovery from APFS drives can be more challenging than with older file systems like HFS+. The metadata structure of APFS, which improves performance and reliability, also makes traditional data recovery tools less effective without updates or new approaches.
Limited time-tested stability. As a relatively new file system, APFS hasn't been tested over time as extensively as more established file systems like NTFS or HFS+. Early versions faced bugs and stability issues, although many of these have been addressed in subsequent updates.
Performance on HDDs. While APFS is optimized for SSDs (solid-state drives), its performance on HDDs (hard disk drives) can be less impressive. Users have reported slower performance on mechanical drives compared to SSDs, likely due to APFS's optimization for the faster access times of solid-state technology.
Lack of full disk compression. Unlike some other file systems, APFS does not natively support full disk compression. This can be a disadvantage for users who need to manage storage space more efficiently, particularly on devices with limited disk capacity.
Overhead of snapshots and clones. While the snapshot and cloning features of APFS are useful for backing up and restoring data, they can also lead to increased storage usage over time. Users need to manage snapshots carefully to avoid inadvertently consuming excessive disk space.
Encryption complexity. Managing encryption with APFS, especially with multi-key encryption configurations, can be complex and may require a deeper understanding of the system’s settings and options.

APFS vs. HFS+

APFS (Apple File System) and HFS+ (Hierarchical File System Plus) are two generations of file systems used by Apple, with APFS being the newer of the two, introduced to replace HFS+.

APFS is designed with modern storage technologies in mind, being specifically optimized for solid-state drives (SSDs) and featuring robust capabilities like native encryption, space sharing, and snapshots. This file system is structured to enhance performance and reliability in today’s diverse computing environments, providing faster access times and improved data integrity compared to its predecessor. Additionally, APFS's architecture allows for more efficient space utilization and offers better support for large storage volumes, which is crucial given the increasing data demands of contemporary applications. In contrast, HFS+, developed in 1998, was an improvement over the original HFS and was Apple's primary file system for nearly two decades. While HFS+ introduced several advanced features at the time, such as journaling to improve reliability and support for larger files, it lacks many of the optimizations that are critical for the latest hardware technologies. For instance, HFS+ does not handle the allocation of storage space as efficiently as APFS, which can lead to issues like file fragmentation and slower performance on newer SSDs. Moreover, HFS+ does not support features like cloning, snapshots, and multi-key encryption, which are integral to APFS. Despite its proven reliability, HFS+ does not scale as well with the high storage capacities and security requirements of current devices, making APFS a more suitable option for modern macOS, iOS, and other Apple operating systems.