Using Raw Data Slices

The SunOS operating system stores the disk label in block 0 of each disk. So, third-party database applications that create raw data slices must not start at block 0, or 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:

• Block 0 where the disk label is stored

• Slice 2, which represents the entire disk

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.

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

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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 operating system software 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 operating system software.

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:

• Servers

• Standalone systems

Each system configuration requires the use of different slices. The following table lists these requirements.

Table 31-4 System Configurations and Slice Requirements

Slice	Servers	Standalone 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".

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Note - The Solaris installation program provides slice size recommendations based on the software you select for installation.

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The format Utility

Read the following overview of the format utility and its uses before proceeding to the "how-to" or reference sections.

The format utility is a system administration tool that is used to prepare hard disk drives for use on your Solaris system.

The following table shows the features and associated benefits that the format utility provides.

Table 31-5 Features and Benefits of the format Utility

Feature	Benefit
Searches your system for all attached disk drives	Reports on the following: Target location Disk geometry Whether the disk is formatted If the disk has mounted partitions
Retrieves disk labels	Convenient for repair operations
Repairs defective sectors	Allows administrators to repair disk drives with recoverable errors instead of sending the drive back to the manufacturer
Formats and analyzes a disk	Creates sectors on the disk and verifies each sector
Partitions a disk	Divides a disk into slices so individual file systems can be created on separate slices
Labels a disk	Writes disk name and configuration information to the disk for future retrieval (usually for repair operations)

The format utility options are fully described in Chapter 35, The format Utility (Reference).

When to Use the format Utility

Disk drives are partitioned and labeled by the Solaris installation program when you install the Solaris release. You can use the format utility to do the following:

• Display slice information

• Divide a disk into slices

• Add a disk drive to an existing system

• Format a disk drive

• Label a disk

• Repair a disk drive

• Analyze a disk for errors

The main reason a system administrator uses the format utility is to divide a disk into disk slices. These steps are covered in Chapter 33, SPARC: Adding a Disk (Tasks) and Chapter 34, IA: Adding a Disk (Tasks).

See the following section for guidelines on using the format utility.

Guidelines for Using the format Utility

Table 31-6 The format Utility Guidelines

Task	Guidelines	For More Information
Format a disk	Any existing data is destroyed when you reformat a disk. The need for formatting a disk drive has dropped as more and more manufacturers ship their disk drives formatted and partitioned. You might not need to use the format utility when you add a disk drive to an existing system. If a disk has been relocated and is displaying a lot of disk errors, you can attempt to reformat it, which will automatically remap any bad sectors.	"How to Format a Disk"
Replace a system disk	Data from the damaged system disk must be restored from a backup medium. Otherwise, the system will have to be reinstalled by using the installation program.	"SPARC: How to Connect a System Disk and Boot" or "IA: How to Connect a System Disk and Boot" or if the system must be reinstalled, Solaris 9 Installation Guide
Divide a disk into slices	Any existing data is destroyed when you repartition and relabel a disk with existing slices. Existing data must be copied to backup media before the disk is repartitioned and restored.	"SPARC: How to Create Disk Slices and Label a Disk" or "IA: How to Create Disk Slices and Label a Disk"
Add a secondary disk to an existing system	Any existing data must be restored from backup media if the secondary disk is reformatted or repartitioned.	"SPARC: How to Connect a Secondary Disk and Boot" or "IA: How to Connect a Secondary Disk and Boot"
Repair a disk drive	Some customer sites prefer to replace rather than repair defective drives. If your site has a repair contract with the disk drive manufacturer, you might not need to use the format utility to repair disk drives. The repair of a disk drive usually means that a bad sector is added to a defect list. New controllers remap bad sectors automatically with no system interruption. If the system has an older controller, you might need to remap a bad sector and restore any lost data.	"Repairing a Defective Sector"