Chapter 10 Managing Disks (Overview)

This chapter provides overview information about Solaris disk slices and introduces the format utility.

This is a list of overview information in this chapter.

• What's New in Disk Management in the Solaris 9 Update Releases?

• Where to Find Disk Management Tasks

• Overview of Disk Management

• Disk Terminology

• About Disk Slices

• The format Utility

• About Disk Labels

• Dividing a Disk Into Slices

For instructions on how to add a disk to your system, see Chapter 12, SPARC: Adding a Disk (Tasks) or Chapter 13, x86: Adding a Disk (Tasks).

What's New in Disk Management in the Solaris 9 Update Releases?

This section describes new disk management features in this Solaris release.

SPARC: Multiterabyte Disk Support With EFI Disk Label

Solaris 9 4/03 – Provides support for disks that are larger than 1 terabyte on systems that run a 64-bit Solaris kernel.

You can download the EFI specification at http://www.intel.com/technology/efi/main_specification.htm.

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 SPARC: 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 http://docs.sun.com/db/doc/816-2542-10.

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.

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 no partition can start at sector zero (0).

• No cylinder, head, or sector information is stored in the 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 to use disks greater than 1 terabyte is appropriate for your environment:

• The SCSI driver, ssd, currently only supports up to 2 terabytes. If you need greater disk capacity than 2 terabytes, use a volume management product like Solaris Volume Manager to create a larger device.

• Layered software products intended for systems with EFI-labeled disks might be incapable of accessing a disk with an EFI disk label.

• A disk with an EFI disk label is not recognized on systems running previous Solaris releases.

• The EFI disk label is not supported on IDE disks.

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

• 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 disksets with EFI-labeled disks.

• The EFI specification prohibits overlapping slices. The whole disk is represented by cxtydz.

• 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.

Installing a System With an EFI-Labeled Disk

The Solaris installation utilities automatically recognize disks with EFI labels, but cannot use the Solaris installation utilities to repartition these disks. You must use the format utility to repartition this 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 looks 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.

Cloning a Disk with an EFI Label

In previous Solaris releases, slice 2 (s2) was used to represent the whole disk. You could use the dd command to clone or copy disks by using syntax similar to the following:

dd if=/dev/rdsk/c0t0d0s2 of=/dev/rdsk/c0t2d0s2 bs=128k

Now, you must use a slightly different procedure to clone or copy disks larger than 1 terabyte so that the UUID of cloned disks are unique. For example:

1. Use the dd command to clone the disk with an EFI label:

   # dd if=/dev/rdsk/c0t0d0 of=/dev/rdsk/c0t2d0 bs=128k

2. Pipe the prtvtoc output of the disk to be copied to the fmthard command to create a new label for the cloned disk.

   # prtvtoc /dev/rdsk/c0t0d0 | fmthard -s - /dev/rdsk/c0t2d0

If you do not create a new label for the cloned disk, other software products might corrupt data on EFI-labeled disks if they encounter duplicate UUIDs.

Troubleshooting Problems With EFI Disk Labels

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

Error Message

The capacity of this LUN is too large. Reconfigure this LUN so that it is < 2TB.

Cause

You attempted to create a partition on a SCSI device that is larger than 2 terabytes.

Solution

Create a partition on a SCSI device that is less than 2 terabytes.

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 kernel with a disk greater than 1 terabyte.

Solution

Boot a system running a 64-bit SPARC 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 this disk to a system running an older Solaris release.

Solution

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

Where to Find Disk Management Tasks

Use these references to find step-by-step instructions for managing disks.

Overview of Disk Management

The management of disks in the Solaris environment 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 operating system. Occasionally, you might need to use the format utility to add a new disk drive or replace a defective one.

The Solaris operating system runs on two types of hardware, or platforms—SPARC and x86. The Solaris operating system runs on both 64–bit and 32–bit address spaces. The information in this document pertains to both platforms and address spaces unless called out in a special chapter, section, note, bullet, figure, table, example, or code example.

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:

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

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

For information about file systems, see Chapter 15, Managing File Systems (Overview).

Slices are sometimes referred to as partitions. This book uses slice but 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.

Solaris Volume Manager, previously Solstice DiskSuite^TM, has a partitioning feature, soft partitioning, that enables 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 partitioning, see Chapter 12, Soft Partitions (Overview), in Solaris Volume Manager Administration Guide.

SPARC: Disk Slices

The following table describes the slices on a SPARC based system.

x86: Disk Slices

On x86 based systems, disks are divided into fdisk partitions. An fdisk partition is a section of the disk that reserved for a particular operating system, such as the Solaris release.

The Solaris release places ten slices, numbered 0–9, on a Solaris fdisk partition as shown in the following table.

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 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.

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

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

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

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.

The format utility options are fully described in Chapter 14, 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 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

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 accomplishes two steps:

• The disk media is prepared for use

• A list of disk defects based on a surface analysis is compiled

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.

About Disk Labels

A special area of every disk is set aside for storing information about the disk's controller, geometry, and slices. That 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.

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

Partition Table

An important part of the disk label is the partition table, which identifies a disk's slices, the slice boundaries (in cylinders), and the total size of the slices. You can display a disk's partition table by using the format utility. The following table describes partition table terminology.

Partition flags and tags are assigned by convention and require no maintenance.

For more information on displaying the partition table, see How to Display Disk Slice Information or How to Examine a Disk Label.

Displaying Partition Table Information

The following is an example of a partition table from a 4.0-Gbyte disk with a VTOC label displayed from the format utility:

Total disk cylinders available: 8892 + 2 (reserved cylinders)

Part      Tag    Flag     Cylinders        Size            Blocks
  0       root    wm    1110 - 4687        1.61GB    (0/3578/0) 3381210
  1       swap    wu       0 - 1109      512.00MB    (0/1110/0) 1048950
  2     backup    wm       0 - 8891        4.01GB    (0/8892/0) 8402940
  3 unassigned    wm       0               0         (0/0/0)          0
  4 unassigned    wm       0               0         (0/0/0)          0
  5 unassigned    wm       0               0         (0/0/0)          0
  6 unassigned    wm       0               0         (0/0/0)          0
  7       home    wm    4688 - 8891        1.89GB    (0/4204/0) 3972780

The partition table displayed by the format utility contains the following information:

The following is an example of a EFI disk label displayed by using the prtvtoc command.

# prtvtoc /dev/rdsk/c4t1d0s0
* /dev/rdsk/c4t1d0s0 partition map
*
* Dimensions:
*     512 bytes/sector
* 2576941056 sectors
* 2576940989 accessible sectors
*
* Flags:
*   1: unmountable
*  10: read-only
*
*                           First     Sector    Last
* Partition  Tag  Flags     Sector     Count    Sector   Mount Directory
       0      2    00          34   629145600  629145633
       1      4    00   629145634   629145600 1258291233
       6      4    00  1258291234  1318633404 2576924637
       8     11    00  2576924638       16384 2576941021
* Flags:
*   1: unmountable
*  10: read-only
*

The prtvtoc command provides the following information:

Dividing a Disk Into Slices

The format utility is most often used by system administrators to divide a disk into slices. The steps are as follows:

• Determining which slices are needed

• Determining the size of each slice

• Using the format utility to divide the disk into slices

• Labeling the disk with new slice information

• Creating the file system for each slice

The easiest way to divide a disk into slices is to use the modify command from the partition menu of the format utility. The modify command allows you to create slices by specifying the size of each slice without having to keep track of the starting cylinder boundaries. The modify command also keeps tracks of any disk space that remains in the “free hog” slice.

Using the Free Hog Slice

When you use the format utility to change the size of one or more disk slices, you designate a temporary slice that will expand and shrink to accommodate the resizing operations.

This temporary slice donates, or “frees,” space when you expand a slice, and receives, or “hogs,” the discarded space when you shrink a slice. For this reason, the donor slice is sometimes called the free hog.

The free hog slice exists only during installation or when you run the format utility. There is no permanent free hog slice during day-to-day operations.

For information on using the free hog slice, see SPARC: How to Create Disk Slices and Label a Disk or x86: How to Create Disk Slices and Label a Disk.