Overview of Disk Management

Managing disks in the Solaris OS usually involves setting up the system and running the Solaris installation program to create the appropriate disk slices and file systems and to install the Solaris OS. Occasionally, you might need to use the format utility to add a new disk drive or replace a defective disk drive.

Disk Terminology

Before you can effectively use the information in this section, you should be familiar with basic disk architecture. In particular, you should be familiar with the following terms:

Disk Term	Description
Track	A concentric ring on a disk that passes under a single stationary disk head as the disk rotates.
Cylinder	The set of tracks with the same nominal distance from the axis about which the disk rotates.
Sector	Section of each disk platter. A sector holds 512 bytes.
Block	A data storage area on a disk. A disk block is 512 bytes.
Disk controller	A chip and its associated circuitry that controls the disk drive.
Disk label	The first sector of a disk that contains disk geometry and partition information.
Device driver	A kernel module that controls a hardware or virtual device.

For additional information, see the product information from your disk's manufacturer.

About Disk Labels

A special area of every disk is set aside for storing information about the disk's controller, geometry, and slices. This information is called the disk's label. Another term that is used to described the disk label is the VTOC (Volume Table of Contents) on a disk with a VTOC label. To label a disk means to write slice information onto the disk. You usually label a disk after you change its slices.

The Solaris release supports the following two disk labels:

SMI – The traditional VTOC label for disks that are less than 1 terabyte in size.
EFI – Provides support for disks that are larger than 1 terabyte on systems that run a 64-bit Solaris kernel. The Extensible Firmware Interface GUID Partition Table (EFI GPT) disk label is also available for disks less than 1 terabyte that are connected to a system that runs a 32-bit Solaris kernel.

If you fail to label a disk after you create slices, the slices will be unavailable because the OS has no way of “knowing” about the slices.

EFI Disk Label

The EFI label provides support for physical disks and virtual disk volumes. This release also includes updated disk utilities for managing disks greater than 1 terabyte. The UFS file system is compatible with the EFI disk label, and you can create a UFS file system greater than 1 terabyte. For information on creating a multiterabyte UFS file system, see 64-bit: Support of Multiterabyte UFS File Systems.

The unbundled Sun QFS file system is also available if you need to create file systems greater than 1 terabyte. For information on the Sun QFS file system, see Sun QFS, Sun SAM-FS, and Sun SAM-QFS File System Administrator’s Guide.

The Solaris Volume Manager software can also be used to manage disks greater than 1 terabyte in this Solaris release. For information on using Solaris Volume Manager, see Solaris Volume Manager Administration Guide.

The VTOC label is still available for disks less than 1 terabyte in size. If you are only using disks smaller than 1 terabyte on your systems, managing disks will be the same as in previous Solaris releases. In addition, you can use the format-e command to label a disk less than 1 terabyte with an EFI label. For more information, see Example 11-6.

You can use the format -e command to apply an EFI label to a disk if the system is running the appropriate Solaris release. However, you should review the important information in Restrictions of the EFI Disk Label before attempting to apply an EFI label.

Comparison of the EFI Label and the VTOC Label

The EFI disk label differs from the VTOC disk label in the following ways:

Provides support for disks greater than 1 terabyte in size.
Provides usable slices 0-6, where slice 2 is just another slice.
Partitions (or slices) cannot overlap with the primary or backup label, nor with any other partitions. The size of the EFI label is usually 34 sectors, so partitions start at sector 34. This feature means that no partition can start at sector zero (0).
No cylinder, head, or sector information is stored in the EFI label. Sizes are reported in blocks.
Information that was stored in the alternate cylinders area, the last two cylinders of the disk, is now stored in slice 8.
If you use the format utility to change partition sizes, the unassigned partition tag is assigned to partitions with sizes equal to zero. By default, the format utility assigns the usr partition tag to any partition with a size greater than zero. You can use the partition change menu to reassign partition tags after the partitions are changed. However, you cannot change a partition with a non-zero size to the unassigned partition tag.

Restrictions of the EFI Disk Label

Keep the following restrictions in mind when determining whether using disks greater than 1 terabyte is appropriate for your environment:

Layered software products intended for systems with VTOC-labeled disks might be incapable of accessing a disk with an EFI disk label.
A disk with an EFI label is not recognized on systems running previous Solaris releases.
You cannot boot from a disk with an EFI disk label.
You cannot use the fdisk command on a disk with an EFI label that is greater than 1 terabyte in size.
You cannot use the Solaris Management Console's Disk Manager tool to manage disks with EFI labels. Use the format utility to partition disks with EFI labels. Then, you can use the Solaris Management Console's Enhanced Storage Tool to manage volumes and disk sets with EFI-labeled disks.
The EFI specification prohibits overlapping slices. The entire disk is represented by cxtydz.
The EFI disk label provides information about disk or partition sizes in sectors and blocks, but not in cylinders and heads.
The following format options are either not supported or are not applicable on disks with EFI labels:
- The save option is not supported because disks with EFI labels do not need an entry in the format.dat file.
- The backup option is not applicable because the disk driver finds the primary label and writes it back to the disk.

Support for EFI-Labeled Disks on x86 Systems

Solaris support for the EFI disk label is available on x86 systems. Use the following command to add an EFI label on an x86 system:

# format -e
> [0] SMI Label
> [1] EFI Label
> Specify Label type[0]: 1
> WARNING: converting this device to EFI labels will erase all current
> fdisk partition information. Continue? yes

Previous label information is not converted to the EFI disk label.

You will have to recreate the label's partition information manually with the format command. You cannot use the fdisk command on a disk with an EFI label that is greater than 1 terabyte in size. The fdisk command is not intended for disks that are larger than 1 terabyte. For more information about EFI disk labels, see the preceding section.

Installing a System With an EFI-Labeled Disk

The Solaris installation utilities automatically recognize disks with EFI labels. However, you cannot use the Solaris installation program to repartition these disks. You must use the format utility to repartition an EFI-labeled disk before or after installation. The Solaris Upgrade and Live Upgrade utilities also recognize a disk with an EFI label. However, you cannot boot a system from an EFI-labeled disk.

After the Solaris release is installed on a system with an EFI-labeled disk, the partition table appears similar to the following:

Current partition table (original):
Total disk sectors available: 2576924638 + 16384 (reserved sectors)

Part      Tag    Flag     First Sector          Size          Last Sector
  0       root    wm                34         1.20TB           2576924636
  1 unassigned    wm                 0            0                0    
  2 unassigned    wm                 0            0                0    
  3 unassigned    wm                 0            0                0    
  4 unassigned    wm                 0            0                0    
  5 unassigned    wm                 0            0                0    
  6 unassigned    wm                 0            0                0    
  8   reserved    wm        2576924638         8.00MB           2576941021

Managing Disks With EFI Disks Labels

Use the following table to locate information on managing disks with EFI disk labels.

Task	For More Information
If the system is already installed, connect the disk to the system and perform a reconfiguration boot.	SPARC: Adding a System Disk or a Secondary Disk (Task Map) or x86: Adding a System Disk or a Secondary Disk (Task Map)
Repartition the disk by using the `format` utility, if necessary.	SPARC: How to Create Disk Slices and Label a Disk or x86: How to Create Disk Slices and Label a Disk
Create disk volumes, and if needed, create soft partitions by using Solaris Volume Manager. Or, set up a ZFS storage pool.	Chapter 2, Storage Management Concepts, in Solaris Volume Manager Administration Guide or Creating a ZFS Storage Pool in ZFS Administration Guide
Create UFS file systems for the new disk by using the `newfs` command.	SPARC: How to Create a UFS File System or x86: How to Create File Systems
Or, create a ZFS file system.*	How to Create ZFS File Systems in ZFS Administration Guide
Clone a disk with an EFI label	Example 29-2

*If a ZFS file system or UFS file system does not meet your needs, consider a QFS file system.

Troubleshooting Problems With EFI Disk Labels

Use the following error messages and solutions to troubleshoot problems with EFI-labeled disks.

Error Message

Dec  3 09:26:48 holoship scsi: WARNING: /sbus@a,0/SUNW,socal@d,10000/
sf@1,0/ssd@w50020f23000002a4,0 (ssd1):
Dec  3 09:26:48 holoship disk has 2576941056 blocks, which is too large 
for a 32-bit kernel

Cause

You attempted to boot a system running a 32-bit SPARC or x86 kernel with a disk greater than 1 terabyte.

Solution

Boot a system running a 64-bit SPARC or x86 kernel with a disk greater than 1 terabyte.

Error Message

Dec  3 09:12:17 holoship scsi: WARNING: /sbus@a,0/SUNW,socal@d,10000/
sf@1,0/ssd@w50020f23000002a4,0 (ssd1):
Dec  3 09:12:17 holoship corrupt label - wrong magic number

Cause

You attempted to add a disk to a system running an older Solaris release.

Solution

Add the disk to a system running the Solaris release that supports the EFI disk label.

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 Solaris OS (and to the system administrator) as though it were a separate disk drive.

For information about file systems, see Chapter 17, 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:

Each disk slice holds only one file system.
No file system can span multiple slices.

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 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^TM, 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 Solaris OS.

On x86 systems:

Disks are divided into fdisk partitions. An fdisk partition is a section of the disk that is reserved for a particular operating system, such as the Solaris OS.
The Solaris OS places ten slices, numbered 0-9, on a Solaris fdisk partition.

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 and Live Upgrade, 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:

Block 0 where the disk label is stored
Slice 2, which represents the entire disk with a VTOC label

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:

Servers
Stand-alone systems

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.

`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 10-4 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 that 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 described in Chapter 16, The format Utility (Reference).

When to Use the `format` Utility

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

Display slice information
Partition a disk
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 partition a disk. These steps are covered in Chapter 12, SPARC: Adding a Disk (Tasks) and Chapter 13, x86: Adding a Disk (Tasks).

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

Guidelines for Using the `format` Utility

Table 10-5 `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 decreased 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 many disk errors, you can attempt to reformat it. Reformatting automatically remaps 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 utility.	SPARC: How to Connect a System Disk and Boot, x86: How to Connect a System Disk, or, if the system must be reinstalled, Solaris Express Installation Guide: Basic Installations
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 x86: 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 x86: 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 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

Formatting a Disk

In most cases, disks are formatted by the manufacturer or reseller. So, they do not need to be reformatted when you install the drive. To determine if a disk is formatted, use the format utility. For more information, see How to Determine if a Disk Is Formatted.

If you determine that a disk is not formatted, use the format utility to format the disk.

When you format a disk, you accomplish two steps:

The disk media is prepared for use.
A list of disk defects based on a surface analysis is compiled.

Caution - Formatting a disk is a destructive process because it overwrites data on the disk. For this reason, disks are usually formatted only by the manufacturer or reseller. If you think disk defects are the cause of recurring problems, you can use the format utility to do a surface analysis. However, be careful to use only the commands that do not destroy data. For details, see How to Format a Disk.

A small percentage of total disk space that is available for data is used to store defect and formatting information. This percentage varies according to disk geometry, and decreases as the disk ages and develops more defects.

Formatting a disk might take anywhere from a few minutes to several hours, depending on the type and size of the disk.