Blocks

Represents the physical on-disk location of data, covering a group of sectors. A block is the smallest amount of disk space that can be allocated to a given File.

Block size and allocation is dependent on the Filesystem; in general, larger blocks = reduced file management overhead but also reduces the maximum number of files that can be stored on disk.

E.g.

• ext4 uses default block sizes of 4KiB
• ntfs has a default “cluster” (block) size of 4KiB
• Older file systems (e.g. hfs+) use default block sizes of 512b

The file system may then aggregate blocks into groups - e.g. ext4 combines blocks into block groups, with a Block Group Descriptor Table