![hfs file system reader hfs file system reader](https://www.maketecheasier.com/assets/uploads/2016/10/apfs-cloning.png)
All of the allocation blocks containing the volume header, alternate volume header and the reserved areas are marked as used in the allocation file. The first 1024 bytes of volume (before the volume header), and the last 512 bytes of the volume (after the alternate volume header) are reserved. A copy of the volume header, known as the alternate volume header, is also stored starting at 1024 bytes before the end of the volume. The volume header is always located at 1024 bytes from the start of the volume. Volume headerĮvery HFS Plus volume has a volume header, which contains information about the volume, such as the date and time of the volume’s creation and the number of files on the volume, as well as the location of the other key structures on the volume. Files and directories also contain a small amount of additional information (known as catalog information or metadata) such as the modification date or Finder info. The size (in bytes) of an allocation block is a power of two, greater than or equal to 512, which is set when the volume is initialized.įiles on an HFS volume have two components or forks: a data fork and a resource fork, either of which may be empty (zero length). HFS Plus allocates space in units known as allocation blocks, which is simply a group of consecutive bytes.
![hfs file system reader hfs file system reader](https://i0.wp.com/swissmacuser.ch/wp-content/uploads/2020/02/macOS-Disk-Utility-cannot-mount-Apple_HFS-error-Teaser.png)
HFS Plus is a specification of how a volume (files that contain user data, along with the structure to retrieve that data) exists on a disk (the medium on which user data is stored). However, HFS+ itself was also replaced with the Apple File System (APFS), released with macOS High Sierra in 2017.
#HFS FILE SYSTEM READER MAC OS#
HFSPlus, also known as Mac OS Extended, replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with Mac OS 8.1 in 1998.