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.

The following information is described in this section:

Disk Terminology
About Disk Labels
EFI (GPT) Disk Label
About Disk Slices
format Utility

Disk Terminology

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

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.
Block	A data storage area on a disk.
Disk controller	A chip and its associated circuitry that controls the disk drive.
Disk label	Part of the disk, usually starting from first sector, that contains disk geometry and partition information.
Device driver	A kernel module that controls a physical (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 or partitions.

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 (GPT) 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 disk utilities for managing disks greater than 2 TB in size.

Starting in Oracle Solaris 11.1, the system is installed with an EFI (GPT) labeled disk on SPARC systems with GPT enabled firmware and x86 systems by default. For more information, see Installing a System With an EFI-Labeled Disk.

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

The Oracle Solaris ZFS file system supports file systems that are greater than 1 TB in size.
The legacy Solaris Volume Manager software can also be used to manage disks that are greater than 1 TB, but a root disk that is managed by Solaris Volume Manager cannot be used for booting the Oracle Solaris 11 release. For information on using Solaris Volume Manager, see Solaris Volume Manager Administration Guide.

You can use the format -e command to apply an EFI label to a disk, if the system is running a supported 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.

When using the format -e command on an EFI (GPT) labeled disk, the partition menu displays 128 partitions (slices), but only 7 partitions are usable.

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 partition 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).
EFI (GPT) labels do not use the notion of geometry. The partitions are defined based on logical blocks.
Some information that was stored in the alternate cylinder area is now stored in the last two cylinders of a disk or Solaris partition.
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 2 terabytes is appropriate for your environment:

Layered software products that are intended for systems with VTOC-labeled disks might be incapable of accessing 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 partitions. 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 to 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.

x86: Support for EFI-Labeled Disks

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 a 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

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

In Oracle Solaris 11.1, in most cases, when the system is installed, an EFI (GPT) label is applied automatically to the root pool disk on SPARC systems with GPT enabled firmware and x86 based systems. For example:

# zpool status rpool
   pool: rpool
 state: ONLINE
  scan: none requested
config:

        NAME      STATE     READ WRITE CKSUM
        rpool     ONLINE       0     0     0
          c8t2d0  ONLINE       0     0     0

After installation on an x86 based system, a root pool disk might look similar to the following:

# prtvtoc /dev/dsk/c8t2d0
* /dev/dsk/c8t2d0 partition map
*
* Dimensions:
*     512 bytes/sector
* 143374738 sectors
* 143374671 accessible sectors
*
* Flags:
*   1: unmountable
*  10: read-only
*
* Unallocated space:
*       First     Sector    Last
*       Sector     Count    Sector
*          34       222       255
*
*                          First     Sector    Last
* Partition  Tag  Flags    Sector     Count    Sector  Mount Directory
       0     24    00        256    524288    524543
       1      4    00     524544 142833777 143358320
       8     11    00  143358321     16384 143374704
root@sys-04:~#

On an x86 system, in addition to the traditional partition 8, a small partition 0 is created to contain the boot loader. Similar to partition 8, this slice requires no administration and should be left alone. The root file system is contained in partition 1.

The zpool command has been modified to create a new root pool disk label automatically, if you need to recreate a root pool after the system is installed. For more information, see Chapter 4, Managing ZFS Root Pool Components, in Oracle Solaris 11.1 Administration: ZFS File Systems.

Managing Disks With EFI Labels

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

Task	For More Information
If the system is not installed, install it.	Installing Oracle Solaris 11.1 Systems
The system is already installed, but the root pool disk was damaged or needs to be replaced.	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
The system is already installed, but you need to set up a disk for a non-root pool.	SPARC: How to Set Up a Disk for a ZFS Non-Root File System or x86: How to Set Up a Disk for a ZFS Non-Root File System

Troubleshooting Problems With EFI Disk Labels

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

Cause

Boot a system running a 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 that are 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 that are 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 14, 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.

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 describes the features and associated benefits of the format utility.

Table 7-1 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 or partitions. ZFS file systems do not correspond to disk slices or partitions, 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 13, 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 Oracle Solaris. You can use the format utility to do the following:

Display slice or partition 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 10, Setting Up Disks (Tasks) and x86: Setting Up Disks for ZFS File Systems (Task Map).

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

Guidelines for Using the `format` Utility

Table 7-2 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 11.1 Systems
Create a VTOC labeled disk slice for a root pool on a SPARC based system. Or, create an EFI labeled disk partition for a root pool on x86 based system.	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 on a SPARC based system, 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 Set Up a Disk for a ZFS Root File System
Set up a disk that contains a ZFS non-root 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 Non-Root File System or x86: How to Set Up a Disk for a ZFS Non-Root 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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