This B-tree contains entries for each volume with its ID and offset. To map block IDs to block offsets a pointer to a block map B-tree is stored. Additionally the block IDs of all volumes are stored in the superblock. The CS contains information on the blocksize, the number of blocks and pointers to the space manager for this task. Because of the structure with containers and flexible volumes, allocation needs to be handled on container level. The CS (Container Superblock) is the entry point to the filesystem. Other informations in the header include the copy-on-write version of the block, the block id and the block type. This header starts with a checksum for the whole block. Block headerĮach filesystem structure in ApFS starts with a block header. Partitions formatted in ApFS are not recognized by OS X 10.11 Yosemite and earlier versions of the operating system. The new file system will be released for widespread use next year, and by that time, developers need to prepare to transfer the utilities to the new file system. This is not a complete list of the innovations that ApFS will bring. The user can use several encryption keys to ensure data security even in the case of “physical compromise” of the medium. This will reduce the number of failures in data transfer and other file operations.ĪpFS has a built-in encryption system and uses AES-XTS or AES-CBC systems, depending on the device. In HFS+ timestamps were set to the nearest second. The new file system uses nanoseconds to set timestamps.

With a 64-bit index, ApFS volumes will support up to 9 quintillion (1018) files. Each container contains one or more volumes or file systems, each of which has its own namespace, that is, a set of files and directories.ĪpFS does not directly support software RAID, but it can be used with Apple RAID volumes to support Striping (RAID 0), Mirroring (RAID 1), and Concatenation (JBOD).

They have their own crash protection and disk space allocation scheme. The following types exist:Ĭontainers are usually exactly the same as the GUID Partition Table (GPT) entries. Afterwards the body of the structure is following. This image shows an overview of the ApFS structure:Įach element of this structure (except for the allocation file) starts with a 32 byte block header, which contains some general information about the block. It needs to be > 512 Mb to contain more than one volume, > 1024Mb to contain more than 2 volumes and so on. Also a container is the primary object for storing data. Contents ApFS Structure Containers and VolumesĪpFS is structured in a single container that can contain multiple ApFS volumes.

Mac disk image vs volume vs container