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Today Apple officially released macOS High Sierra.
Editor’s Note:
Today Apple officially released macOS High Sierra. In this new version, a very important change is that Apple has brought the new generation file system APFS (Apple File System), which was introduced in iOS 10.3, to macOS.
This file system, developed specifically for SSDs and flash storage, is an upgrade to Apple’s nearly decade-old HFS+ file system. It offers faster response times and improved security. What changes does APFS bring? Why does Apple update to APFS? This article will explain all of these in detail.
What changes does APFS bring?
Currently on-sale Mac and iOS devices use SSD storage based on flash memory. Compared to mechanical hard drives, SSDs have no movable magnetic heads, which allows instant access to any part of the disk, so there is no longer any need to worry about performance degradation caused by “disk fragmentation.” However, at the same price, SSD capacity is much smaller than mechanical hard drives, so it is necessary to save space as much as possible. APFS introduces a lot of targeted technological innovations for SSDs, changing the traditional concepts of “copying” and “backing up.”
File Clones (Clones): copies no longer take up space
Traditionally, copying a 100MB file meant spending an extra 100MB of space to store the second copy. But under APFS, “copying” only creates a new pointer without occupying more space. If one of the files is modified, APFS keeps the unchanged parts and only stores the changes. Copying becomes extremely fast and power-efficient. This means if you copy a 1GB file 10 times, under the old HFS+, the system stores 10 separate backups occupying 10GB of disk space. However, under APFS, even if you copy it 100 times, that file only occupies 1GB on your device.
Before iOS 10.3, due to the sandbox mechanism, if a file in App A needed to be accessed by App B, it had to be copied again, taking double the space. This issue will be completely resolved in APFS.
Disk Snapshots (Snapshot): backups made easy in an instant
More and more people are used to backing up their files and disks to recover from problems. Based on the principle of Clones, APFS introduces Snapshot technology for backups, recording file states at specific moments. Since such backups are incremental, only the changed parts take up more space, so you can back up data more frequently without worrying about filling up your disk.
Similarly, when applied to Time Machine, this technology improves backup speed and efficiency.
Space Sharing: no more worries about full partitions
When using PCs, many people have experienced the embarrassment of a “C drive full” message. In traditional partition schemes, when one partition runs out of space, the free space of other partitions cannot be used to solve the problem. APFS’s new Space Sharing technology virtualizes traditional partitions as Containers. If several containers exist on one APFS disk, each can freely expand or shrink (up to the disk’s theoretical capacity). Whenever any partition runs low on space, the redundant space across the entire APFS volume can be dynamically allocated, so you never have to worry about “insufficient space” prompts during downloads.
I/O Quality of Service (I/O QoS): visible performance improvements
APFS also enhances overall system performance on SSDs by offering technologies like an extensible block allocator, optimized for larger SSD capacities. With I/O QoS (Quality of Service), APFS significantly reduces latency by prioritizing data access requests based on their importance. APFS prioritizes operations that users can clearly perceive, making the device feel noticeably faster.
Beyond new file storage technology, APFS improves security compared to HFS+ in two aspects: encryption and usability.
Encryption technology: no fear even if the device is lost
Previous versions of Mac OS and iOS already offered various data encryption methods. APFS unifies these into three encryption options:
- No encryption
- Single-key encryption
- Multi-key encryption
The multi-key mode means you can encrypt the device with key A, then encrypt some data separately with key B. Even if your device hardware falls into the wrong hands, attackers only get access to data unlocked by key A; without key B, the protected data remains safe forever. This technology also solves a long-standing problem: previously, when switching devices, users were advised to repeatedly overwrite disks with meaningless data for privacy reasons. In the future, simply deleting the key is sufficient without rewriting data multiple times.
Crash Protection: low risk of data corruption
What if the power cuts out while editing a document, and the file can’t be opened? APFS introduces a Copy-on-Write mechanism, where original data is never immediately modified during editing. Modifications are written to a new location first, and the old data is deleted only after the new data is confirmed complete.
Similarly, during device upgrades to APFS, data conversion occurs in free disk space before overwriting old data. Even if a system crash or accidental drop occurs during upgrade, data safety is maximized.
Why does Apple update to APFS?
Before APFS, Apple’s file management system went through three generations. Early Macs used the MFS (Macintosh File System), but soon Apple found that Mac users were creating increasingly large and complex files. In 1985, Apple launched HFS (Hierarchical File System), which became the foundation of Mac file systems for decades. In 1998, Apple upgraded HFS to HFS+ (also called OS X Extended). HFS+ remains the standard Mac file system and also underpins iPod and iOS devices.
In computing, a 30-year-old technology is not in its prime but nearing obsolescence. Over 30 years, Apple has evolved from a computer manufacturer into a flourishing ecosystem. The appearance of APFS is meant to support this entire ecosystem.
Supporting the latest software and hardware technologies
When Apple announced APFS at WWDC 2016, they bluntly stated that HFS+ and its predecessor HFS were designed for floppy disks and mechanical hard drives, thinking only in KB and MB-scale files. Today is the era of SSDs and TB or even PB-scale data, and storage hardware innovation demands a new file system. Furthermore, HFS+ once made tradeoffs for older hardware designs, such as using a global lock on metadata so that only one process can update the file system at a time, which was an optimization for then slow CPUs but now becomes a burden on modern multi-core high-performance processors.
Additionally, mobile internet development has greatly changed device usage scenarios and forms. Common mobile problems like unexpected bugs and power outages have raised new demands for data security, and emerging cybersecurity incidents have heightened encryption standards.
Coordinating and unifying the ecosystem
For Apple, APFS also carries the responsibility of unifying the ecosystem. Before iOS 10.3, although iOS devices used the HFS+ file system, their implementations and functionalities differed across devices. The Mac and iOS product lines had differing codes, creating confusion for developers.
At WWDC, Apple used the term “ending the confusion.” APFS will maintain consistency across all Apple products ranging from Apple Watch to Mac Pro, consolidating code completely. This unification simplifies maintenance, updates, and API calls for developers, and ensures new technologies are equally enjoyed across devices.
In any case, Apple’s use of APFS is inevitable. Apple officially states APFS has excellent compatibility with HFS+, so users won’t encounter unusable programs. The only caveat is that APFS partitions can’t be recognized by older versions of Mac OS, so if you format removable storage as APFS, friends with older systems may not be able to read it. A new era belonging to APFS is coming—it’s time to embrace the future with open arms.
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