Overview of Disk Management

Managing disks in the Oracle Solaris OS usually involves setting up the system and running the Oracle Solaris installation program to create the appropriate disk slices and file systems and to install the Oracle 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 Oracle Solaris release supports the following two disk labels:

SMI – The traditional VTOC label for disks that are less than 2 TB in size.
EFI – Provides support for disks that are larger than 2 TB. The Extensible Firmware Interface GUID Partition Table (EFI GPT) disk label is also available for disks less than 2 TB.

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 that are greater than 2 TB in size. This release also includes updated disk utilities for managing disks greater than 2 TB in size.

The following file system products support file systems greater than 1 TB in size:

The Oracle Solaris ZFS file system supports file systems greater than 1 TB in size.

The VTOC label is still available for disks less than 2 terabytes in size. If you are only using disks smaller than 2 TB 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 2 TB in size or less with an EFI label. For more information, see Example 11-5.

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

You can also use the format -e command to reapply a VTOC label if the EFI label is no longer needed. For example:

# format -e
Specify disk (enter its number): 2
selecting c0t5d0
[disk formatted]
.
.
.
format> label
[0] SMI Label
[1] EFI Label
Specify Label type[1]: 0
Warning: This disk has an EFI label. Changing to SMI label will erase all
current partitions.
Continue? yes
Auto configuration via format.dat[no]? 
Auto configuration via generic SCSI-2[no]? 
format> quit

Caution - Keep in mind that changing disk labels will destroy any data on the disk.

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 2 terabytes 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 usually start at sector 34. This feature means that no partition can start at sector zero (0).
No cylinder 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.
On x86 based systems, you can use the fdisk command on a disk with an EFI label that is greater than 2 TB in size.
Use the format utility to partition disks with EFI labels.
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

Oracle 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 2 terabytes in size. If the fdisk command is run on disk that is greater than 2 TB in size to create a Solaris partition, the Solaris partition is limited to 2 TB. For more information about EFI disk labels, see the preceding section.

Installing a System With an EFI-Labeled Disk

An Oracle Solaris root pool disk must have an SMI label. The Oracle Solaris 11 installation utilities automatically relabel any disk that is selected as a root pool disk with an SMI label.

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.	SPARC: Setting up Disks for ZFS File Systems (Task Map) or x86: Setting Up Disks for ZFS File Systems (Task Map)
Create a ZFS file system.	SPARC: Setting Up Disks for ZFS File Systems or x86: Setting Up Disks for ZFS File Systems

Troubleshooting Problems With EFI Disk Labels

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

Solution

Boot a system running 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 Oracle 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 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

Disk Slices

On a system with ZFS file systems, disk slices are only required for the ZFS root pool that contains the ZFS root file system. In general, the ZFS root pool is contained in slice 0. The ZFS root pool must exist on a slice or mirrored slices because of a long-standing boot limitation. For non-root storage pools, you can use whole disks. ZFS file systems do not correspond to specific disk slices. Managing whole disks is easier than managing disks with slices.

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 Oracle Solaris OS.
The Oracle Solaris OS places ten slices, numbered 0-9, on a Solaris fdisk partition.

Note - On a disk with a VTOC label, do not modify slice or use slice 2 to store a file system. The installgrub command does 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

`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 Oracle Solaris system.

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

Table 10-2 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. ZFS file systems do not correspond to disk slices except for the ZFS root pool.
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 Oracle Solaris installation utility when you install the Oracle 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: Setting Up Disks (Tasks) and Chapter 13, x86: Setting Up Disks (Tasks).

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

Guidelines for Using the `format` Utility

Table 10-3 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 or replace a disk drive to an existing system. If a disk has been relocated and is displaying many disk errors, you can attempt to relabel it.	How to Format a Disk or How to Label a Disk
Set up a disk that contains a ZFS root file system.	In a non-redundant configuration, a ZFS root file system data from the damaged disk must be restored from a backup medium. Otherwise, the system will have to be reinstalled by using the installation utility.	SPARC: How to Set Up a Disk for a ZFS Root File System or x86: How to Set Up a Disk for a ZFS Root File System, or, if the system must be reinstalled, Installing Oracle Solaris 11 Systems
Create a disk slice for a root pool.	The best way to use a ZFS storage pool is by creating a pool with whole disks. If a disk is intended to be used for a root pool, you must create a disk slice. This is long-standing boot limitation.	SPARC: How to Create a Disk Slice for a ZFS Root File System or x86: How to Create a Disk Slice for a ZFS Root File System
Set up a disk that contains a ZFS file system.	A disk that is used for a non-root ZFS file system usually contains space for user or data files. You can attach or add a another disk to a root pool or a non-root pool for more disk space.	SPARC: How to Set Up a Disk for a ZFS File System or x86: How to Set Up a Disk for a ZFS File System

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.

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