When you create a UFS file system, the disk slice is divided into cylinder groups, which are made up of one or more consecutive disk cylinders. The cylinder groups are then further divided into addressable blocks to control and organize the structure of the files within the cylinder group. Each type of block has a specific function in the file system. See "The Structure of UFS File System Cylinder Groups" for more detailed information about each type of block.
If you want to customize a file system using arguments with the newfs command or the mkfs command, see Chapter 40, UFS File System Reference for information about altering these parameters.