Disk Slices (or Partitions)

A single range of contiguous blocks or a physical subset of a disk is known as a disk partition in the SunOS release 4 software. In the SunOS release 5 software, a physical subset of a disk is known as a disk slice. Before you can create a file system on a disk, you must format and divide it into slices. This is usually done when the Solaris release is installed using the Solaris 2 installation program. See System Administration Guide, Volume I if you need to install and format a disk after installation.

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Note -

In some Solaris documentation, Solaris slices are still referred to as "partitions". The Solaris 2 documentation distinguishes between fdisk partitions (for Intel systems) and the divisions within an fdisk partition, referred to interchangeably as slices or partitions.

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See System Administration Guide, Volume I for information about Solaris fdisk partitions.

A slice can be used as a raw device for swap space or to hold one and only one UFS file system, unless you are using a product like Solstice DiskSuite^TM. Table 2-1 describes how disk slices can be set up on each Solaris 2 platform.

Table 2-1 Slice Differences on Platforms

SPARC	Intel-based
The whole disk is devoted to the Solaris operating environment.	The disk is divided into four fdisk partitions, one per operating environment.
The disk is divided into eight slices, numbered 0-7.	The Solaris fdisk partition is divided into 10 slices, numbered 0-9. Only 0-7 can be used to store user data.

See System Administration Guide, Volume I for a description of customary disk slice assignments for each platform.

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