Cylinder Groups

A UFS file system is created on a disk slice, which is divided into one or more areas called cylinder groups. A cylinder group is composed of one or more consecutive disk cylinders (the set of tracks on a group of platters that have the same radial distance from the center of the platter). See System Administration Guide, Volume I for a complete description of disk geometry.

A cylinder group map is created for each cylinder group. The cylinder group map records the block usage and available blocks.

Figure 2-1 shows the relationship between disk slices and cylinder groups.

Figure 2-1 Disk Slices and Cylinder Groups