ApFS (stands for Apple File System) is a file system developed by Apple for the new iOS, macOS, tvOS, and watchOS, and is not an add-on or add-on to HFS +. HFS + components: log, distribution file, catalog file, extent overflow file, attribute file have been completely removed from ApFS. This is a revised FS, it uses a different structure and a new data protection policy.
According to the developers, it is optimized as much as possible for SSD and Flash drives. And also, received several nice features: new encryption algorithms, protection against failures, “smart” use of disk space and the function of cloning information. All this provides an increased speed of reading / writing information, stability of the operating system and protection of user data. In practice, additional protection has appeared, but it is not enough.
The ApFS feature is a new read / write algorithm, each unit of data is copied before saving to disk or confirming file changes. That is, the file system stores the “history of changes” of all files, and this allows you to find a large number of structural data blocks of a file, its “pieces”.
The minimum data block size that ApFS processes in this way is 4096 bytes. When found, they are “read”, the metadata is found, and then it is used to extract the files themselves.