Use this tool to display information about a specific disk, create Solaris disk partitions, list partitions, copy the layout of one disk to another disk of the same type, change the disk's Label (descriptive name), create fdisk partitions on an x86 computer, and change the active fdisk partition.
Contained on this page is some background information about a disk and how it is used. For more information, see System Administration Guide: Basic Administration.
To improve disk in/out performance, a disk is formatted -- laid out in a way that groups information and reduces the amount of movement the heads require to read and write information. The layout on the disk is built up of units, from the smallest (the sector) to the largest (the partition).
The smallest unit on a platter is the sector (also called the block), which contains 512 bytes. A series of contiguous sectors makes up a track. The tracks on each platter are concentric, and each track can be read or written to as the disk rotates, without moving the read/write heads.
A cylinder consists of all the tracks that occupy the same position on all of the platters. Because a disk is constantly spinning, and because all the read/write heads move as a unit, the most efficient way for the heads to read and write to the disk is to have all the blocks containing related information located in a single cylinder.
Cylinders themselves are grouped by function. The groups of cylinders are called partitions (also called slices) and are the primary portions of the disk that are administered. On Sun systems, a disk can contain up to eight partitions, labeled 0 through 7. On x86 systems, a disk can contain up to 10 partitions, labeled 0-9. Each partition contains a single file system, and no file system can span multiple partitions.
unassigned - a partition with no named function.
boot
- stores information used for booting the computer.
root
- operating system files and directories (usually
partition 0).
swap
- disk space reserved for swapping program
components in and out of memory, when the programs are too large to
fit entirely in memory (partition 1 is often used).
usr
- contains system commands (executables) to be run
by users (usually partition 6).
backup
- refers to the whole disk (usually partition 2).
stand
- used for standalone programs.
var
- for keeping system files and directories likely to
change in size over the life of the local system, including system
logs, editor backup files, and so forth.
home
- the location for files created by the user
(usually partition 7).
altsctr
- (alternate sector) when a sector is not
written correctly, it is marked as bad and mapped to one in the
altsctr partition.
cache
- a local storage area for data stored on a
server. After remote files are referenced once, they can subsequently
be retrieved from the local cache.