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Translated by OneNewLife What is Apple File System and Why is it Better than HFS.md
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OneNewLife translating.
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# What is Apple File System and Why is it Better than HFS+?
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If you’ve been following the news from Apple’s latest release of macOS, you might have noticed some mention of Apple File System, or APFS. This is one of those wonky topics that don’t get a lot of attention. Yet, it’s the core structure underlying a user’s experience with the operating system. APFS won’t be finalized until 2017, but you can get a taste in the developer preview now available on Sierra.
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### Differences and Improvements
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To review quickly, a file system is the basic structure an operating system uses to store and retrieve data. Different file systems take different approaches to this task. As computers have become faster, newer file systems have taken advantage of the boost to offer new features and adapt to modern storage needs.
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HFS+, the file system that ships with new Macs today, is eighteen years old. HFS, its progenitor, is older than the Tom Cruise bromance flick “Top Gun.” It’s sort of like an old Toyota. It still works (maybe surprisingly well), but it’s not winning any medals.
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APFS isn’t so much an upgrade to HFS+ as it is a quantum leap forward … to the present. Though it’s a major upgrade for Apple users, it seems mostly like Apple is catching up to other systems, rather than overtaking them. Nevertheless, the update isn’t a day too soon.
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### Cloning and Data Integrity
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APFS uses a scheme called copy-on-write to make instant clones of duplicated files. Under HFS+ when a user duplicates a file, every single bit is copied. APFS instead creates a clone by manipulating metadata and allocating disk space. However, no bits are copied until the cloned file is modified. As the clone diverges from the original copy, those changes (and only those changes) are saved.
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Copy-on-write also improves data integrity. Under other systems if your volume unmounts with overwrite operations pending, you might find part of your file system out of sync with the rest. Copy-on-write avoids the problem by writing changes to free disk space instead of overwriting old files. Until the write operation successfully completes, the old file is the canonical version. Only when the new file is successfully copied is the old file purged.
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### System Snapshots
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Snapshots are a major upgrade and are brought to you in part by copy-on-write architecture. A snapshot is a read-only mountable image of a file system at a point in time. As the file system changes, only modified bits are saved. This can make backup simpler and more reliable. Considering the ungainly disappointment of hard links that Time Machine has become, this could be a major upgrade.
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### I/O Quality of Service
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You may have seen the term Quality of Service (QoS) in your router’s setup instructions. QoS prioritizes bandwidth usage to avoid slowing down priority tasks. On your router it employs user-defined rules to give selected tasks the most bandwidth. Reportedly, Apple’s QoS would prioritize user operations such as active windows. Background tasks like Time Machine backups would get demoted. So, maybe less beach balls?
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### Native Encryption
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In a post-Snowden world, encryption is all the rage. And more and more Apple is emphasizing the security of its systems. Built-in, strong encryption comes as no surprise. With APFS, Apple is incorporating a more nuanced encryption scheme than its current, whole-disk-or-nothing approach. Users can use a single key to encrypt all their data or use multiple encryption keys to lock individual files and folders separately. Of course, you could also encrypt nothing, you devil-may-care rascal.
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### SSD & Flash Optimization
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Flash storage optimization has been listed as a headline feature of APFS, but the implementation isn’t thrilling. Rather than taking advantage of their unusual degree of system integration, Apple has instead shifted some of the functions typically handled by the SSD’s chips to the OS. It’s more like the file system is aware of SSDs rather than optimized for them.
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### Dynamic Partition Resizing
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Logical partitions on an APFS drive can dynamically resize themselves. Users need only specify the number of desired partitions. The file system then works out disk allocation on the fly. Each partition only occupies disk space that it’s using to store files. The rest of the disk space is up for grabs by any partition. It’s neat, but it’s a lot more like meta-folders than anything else.
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### Conclusion
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Does this matter? For devs and power users this is awesome. For casual Mac users there shouldn’t be much outward difference. And while the upgrade is great, there are still some missing pieces. Native compression is notably absent, as is checksumming on user data. Of course, anything could change by 2017, so watch this space.
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via: https://www.maketecheasier.com/apple-file-system-better-than-hfs/?utm_medium=feed&utm_source=feedpress.me&utm_campaign=Feed%3A+maketecheasier
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作者： [Alexander Fox][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:https://www.maketecheasier.com/author/alexfox-2-2-2/
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[1]:https://www.maketecheasier.com/apple-file-system-better-than-hfs/#respond
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[3]:https://www.maketecheasier.com/schedule-windows-empty-recycle-bin/
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[4]:https://www.maketecheasier.com/manage-automatic-wordpress-updates/
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[5]:mailto:?subject=What%20is%20Apple%20File%20System%20and%20Why%20is%20it%20Better%20than%20HFS+?&body=https%3A%2F%2Fwww.maketecheasier.com%2Fapple-file-system-better-than-hfs%2F
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[6]:http://twitter.com/share?url=https%3A%2F%2Fwww.maketecheasier.com%2Fapple-file-system-better-than-hfs%2F&text=What+is+Apple+File+System+and+Why+is+it+Better+than+HFS%2B%3F
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[7]:http://www.facebook.com/sharer.php?u=https%3A%2F%2Fwww.maketecheasier.com%2Fapple-file-system-better-than-hfs%2F
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[8]:https://www.maketecheasier.com/category/mac-tips/
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OneNewLife translated.
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# 苹果文件系统比 HFS+ 强在哪里？
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如果你一直关注苹果最新版的 macOS 的消息，你可能已经注意到苹果文件系统，或者说 APFS。这是不太让人感冒的话题之一。然而，它是操作系统用户体验的核心结构。APFS 将在 2017 年之前完成，不过你现在可以在 Sierra（最新版的 macOS） 上面体验一番开发者预览版。
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### 特色与改进
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先快速科普一下，**文件系统** 是操作系统用于存储和检索数据的基本结构，不同的文件系统采用不同的方式来实现这个任务。随着计算机变得越来越快，新生代的文件系统已经利用了提升以提供新功能并适应现代存储需求。
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HFS+，作为今天新一代 Mac 的附带文件系统，已经 18 岁了。它的祖先 HFS 比 Tom Cruise 的兄弟情影片“壮志凌云”还要老。它有点像一辆老丰田。它仍然可以工作（也许惊人的好），但是它不再得到人们的嘉奖。
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APFS 不完全是 HFS+ 的升级版，因为直到现在它已经有一个量子的提升了。虽然这对苹果用户来说是一个重大的升级，但似乎这看起来更像是苹果赶上了其它系统，而不是超越了它们。然而，更新还进展得非常慢。
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### 克隆和数据完整性
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APFS 使用称为写入时复制（copy-on-write）的方案来生成重复文件的即时克隆。在 HFS+ 下，当用户复制文件的时候，每一个位（二进制中的“位”）都会被复制。而 APFS 则通过操作元数据并分配磁盘空间来创建克隆。但是，在修改复制文件之前都不会复制任何位。当克隆与原始副本分离的时候，那些改动（并且只有那些改动）才会被保存。
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写入时复制还提高了数据的完整性。在其它系统下，如果你卸载卷导致覆盖操作挂起的话，你可能会发现你的文件系统有一部分与其它部分不同步。写入时复制则通过将改动写入到可用的磁盘空间而不是覆盖旧文件来避免这个问题。直到写入操作成功完成，旧文件是规范版本。只有当新文件被成功复制时，旧文件才会被清除。
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### 系统快照
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快照是写入时复制架构给你带来的一个主要的升级。快照是文件系统在某个时间点的一个只读的可装载映像。随着文件系统发生改动，只有改动的位会被更改。这可以让备份更简单，更可靠。考虑到时间机器（一个苹果出品的备份工具）已经成为硬链接的痛点，这可能是一个重大的升级。
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### 服务的输入/输出质量
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你可能已经在你的路由器说明书看到了服务质量（QoS）。QoS 优先处理带宽使用以避免降低优先任务的速度。在你的路由器上，它采用用户定义的规则来为指定任务提供最大的带宽。据报道，苹果的 QoS 会优先考虑用户操作，例如活动窗口。而诸如时间机器备份这些后台任务将会被降级。所以，这意味着更少的泡泡了？
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### 本地加密
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在后斯诺登时代，加密成为众矢之的。越来越多的苹果产品正在强调其系统安全性。内置强大的加密机制并不让人感到意外。包括 APFS 在内，苹果正在采用更加细致入微的加密方案，要么不加密，要么就将加密进行到底。用户可以使用单个密钥来为所有数据加密，或者使用多个加密密钥分别锁定单个文件和文件夹。当然，你也可以不加密，只要你对坏蛋无所忌惮。
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### 固态硬盘和闪存优化
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闪存优化已经被列为 APFS 的一个亮点功能，不过它的实现并没有那么振奋人心。苹果选择将固态硬盘的芯片一些一般处理的功能迁移到操作系统，而没有利用深度系统集成。这更像是让文件系统感知固态硬盘，而不是为它们做优化。
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### 动态分区调整
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APFS 驱动器的逻辑分区可以动态调整自身大小。用户只需指定所需分区的数量，然后文件系统会在运行时进行磁盘分配。每个分区只占用其用于存储文件的磁盘空间。剩余的磁盘空间会由任何分区获取。这种设计很整洁，不过比起其它东西，这更像是元文件夹。
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### 结论
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这是否重要？对于开发者和高级用户来说真是棒极了。对于一般的 Mac 用户应该没有太多的外部差异。虽然升级是重大的举措，但仍然存在一些缺失。本地压缩显然还没有，对用户数据进行的校验也没有。当然，2017 年还没到，一切皆有可能，让我们拭目以待。
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编译自: https://www.maketecheasier.com/apple-file-system-better-than-hfs/?utm_medium=feed&utm_source=feedpress.me&utm_campaign=Feed%3A+maketecheasier
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作者： [Alexander Fox][a]
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译者：[OneNewLife](https://github.com/OneNewLife)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:https://www.maketecheasier.com/author/alexfox-2-2-2/
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[1]:https://www.maketecheasier.com/apple-file-system-better-than-hfs/#respond
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[3]:https://www.maketecheasier.com/schedule-windows-empty-recycle-bin/
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[4]:https://www.maketecheasier.com/manage-automatic-wordpress-updates/
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[5]:mailto:?subject=What%20is%20Apple%20File%20System%20and%20Why%20is%20it%20Better%20than%20HFS+?&body=https%3A%2F%2Fwww.maketecheasier.com%2Fapple-file-system-better-than-hfs%2F
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[6]:http://twitter.com/share?url=https%3A%2F%2Fwww.maketecheasier.com%2Fapple-file-system-better-than-hfs%2F&text=What+is+Apple+File+System+and+Why+is+it+Better+than+HFS%2B%3F
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[7]:http://www.facebook.com/sharer.php?u=https%3A%2F%2Fwww.maketecheasier.com%2Fapple-file-system-better-than-hfs%2F
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[8]:https://www.maketecheasier.com/category/mac-tips/
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