test

System Administration Guide: Devices and File Systems

About Disk Slices

Files stored on a disk are contained in file systems. Each file system on a disk is assigned to a slice, which is a group of sectors set aside for use by that file system. Each disk slice appears to the Oracle Solaris OS (and to the system administrator) as though it were a separate disk drive.

For information about file systems, see Chapter 16, Managing File Systems (Overview).

Note –

Slices are sometimes referred to as partitions. Certain interfaces, such as the format utility, refer to slices as partitions.

When setting up slices, remember these rules:

Slices are set up slightly differently on SPARC and x86 platforms. The following table summarizes the differences.

Table 10–1 Slice Differences on SPARC and x86 Platforms

SPARC Platform 

x86 Platform 

The entire disk is devoted to Oracle Solaris OS. 

Disk is divided into fdisk partitions, one fdisk partition per operating system.

VTOC – The disk is divided into 8 slices, numbered 0-7.

EFI – The disk is divided into 7 slices, numbered 0-6.

VTOC – The Solaris fdisk partition is divided into 10 slices, numbered 0–9.

EFI – The disk is divided into 7 slices, numbered 0-6

Solaris Volume Manager, previously the Solstice DiskSuite, has a partitioning feature, soft partitions. Soft partitions enable more than eight partitions per disk.

For general information about Solaris Volume Manager, see Chapter 2, Storage Management Concepts, in Solaris Volume Manager Administration Guide. For information on soft partitions, see Chapter 12, Soft Partitions (Overview), in Solaris Volume Manager Administration Guide.

Disk Slices

The following table describes the slices that might be found on a system that runs the Oracle Solaris OS.

On x86 systems:

Table 10–2 Customary Disk Slices

Slice 

File System 

Usually Found on Client or Server Systems? 

Comments 

0 

root (/)

Both 

Holds files and directories that make up the OS. 

EFI – You cannot boot from a disk with an EFI label.

1 

swap 

Both 

Provides virtual memory, or swap space.

2 

— 

Both 

VTOC – Refers to the entire disk, by convention. The size of this slice should not be changed.

EFI – Optional slice to be defined based on your site's needs.

3 

/export, for example

Both 

Optional slice that can be defined based on your site's needs. 

Can be used on a server to hold alternative versions of operating systems that are required by client systems. 

4 

 

Both 

Optional slice to be defined based on your site's needs. 

5 

/opt, for example

Both 

Optional slice to be defined based on your site's needs. 

Can be used to hold application software added to a system. If a slice is not allocated for the /opt file system during installation, the /opt directory is put in slice 0.

6 

/usr

Both 

Holds OS commands (also known as executables). This slice also holds documentation, system programs (init and syslogd, for example), and library routines.

7 

/home or

/export/home

Both 

Holds files that are created by users. 

8 

N/A 

N/A 

VTOC – Contains GRUB boot information.

EFI – A reserved slice created by default. This area is similar to the VTOC's alternate cylinders. Do not modify or delete this slice.

9 (x86 only)

— 

Both 

EFI – Not applicable.

VTOC – Provides an area that is reserved for alternate disk blocks. Slice 9 is known as the alternate sector slice.

Note –

On a disk with a VTOC label, do not modify slice or use slice 2 to store a file system. Products, such as Solaris Volume Manager, Solaris Live Upgrade, and installgrub, do not work correctly if slice 2 is modified in any way.

Using Raw Data Slices

The disk label is stored in block 0 of each disk. So, third-party database applications that create raw data slices must not start at block 0. Otherwise, the disk label will be overwritten, and the data on the disk will be inaccessible.

Do not use the following areas of the disk for raw data slices, which are sometimes created by third-party database applications:

Slice Arrangements on Multiple Disks

Although a single large disk can hold all slices and their corresponding file systems, two or more disks are often used to hold a system's slices and file systems.

Note –

A slice cannot be split between two or more disks. However, multiple swap slices on separate disks are allowed.

For instance, a single disk might hold the root (/) file system, a swap area, and the /usr file system, while another disk holds the /export/home file system and other file systems that contain user data.

In a multiple disk arrangement, the disk that contains the OS and swap space (that is, the disk that holds the root (/) and /usr file systems and the slice for swap space) is called the system disk. Other disks are called secondary disks or non-system disks.

When you arrange a system's file systems on multiple disks, you can modify file systems and slices on the secondary disks without having to shut down the system or reload the OS.

When you have more than one disk, you also increase input-output (I/O) volume. By distributing disk load across multiple disks, you can avoid I/O bottlenecks.

Determining Which Slices to Use

When you set up a disk's file systems, you choose not only the size of each slice, but also which slices to use. Your decisions about these matters depend on the configuration of the system to which the disk is attached and the software you want to install on the disk.

System configurations that need disk space are as follows:

Each system configuration can use slices in a different way. The following table lists some examples.

Table 10–3 System Configurations and Slices

Slice 

Servers 

Stand-alone Systems 

0 

root 

root 

1 

swap 

swap 

2 

— 

— 

3 

/export

— 

6 

/usr

/usr

7 

/export/home

/home

For more information about system configurations, see Overview of System Types in System Administration Guide: Basic Administration.

Note –

The Solaris installation utility provides default slice sizes based on the software you select for installation.