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Oracle VM Server for SPARC 2.2 Administration Guide     Oracle VM Server for SPARC
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Document Information

Preface

Part I Oracle VM Server for SPARC 2.2 Software

1.  Overview of the Oracle VM Server for SPARC Software

2.  Installing and Enabling Software

3.  Oracle VM Server for SPARC Security

4.  Setting Up Services and the Control Domain

5.  Setting Up Guest Domains

6.  Setting Up I/O Domains

7.  Using Virtual Disks

Introduction to Virtual Disks

Managing Virtual Disks

How to Add a Virtual Disk

How to Export a Virtual Disk Back End Multiple Times

How to Change Virtual Disk Options

How to Change the Timeout Option

How to Remove a Virtual Disk

Virtual Disk Identifier and Device Name

Virtual Disk Appearance

Full Disk

Single-Slice Disk

Virtual Disk Back End Options

Read-only (ro) Option

Exclusive (excl) Option

Slice (slice) Option

Virtual Disk Back End

Physical Disk or Disk LUN

How to Export a Physical Disk as a Virtual Disk

Physical Disk Slice

How to Export a Physical Disk Slice as a Virtual Disk

How to Export Slice 2

File and Volume

File or Volume Exported as a Full Disk

How to Export a File as a Full Disk

How to Export a ZFS Volume as a Full Disk

File or Volume Exported as a Single-Slice Disk

How to Export a ZFS Volume as a Single-Slice Disk

Exporting Volumes and Backward Compatibility

Summary of How Different Types of Back Ends Are Exported

Guidelines for Exporting Files and Disk Slices as Virtual Disks

Configuring Virtual Disk Multipathing

Virtual Disk Multipathing and Virtual Disk Timeout

How to Configure Virtual Disk Multipathing

CD, DVD and ISO Images

How to Export a CD or DVD From the Service Domain to the Guest Domain

How to Export an ISO Image From the primary Domain to Install a Guest Domain

Virtual Disk Timeout

Virtual Disk and SCSI

Virtual Disk and the format Command

Using ZFS With Virtual Disks

Configuring a ZFS Pool in a Service Domain

Storing Disk Images With ZFS

Examples of Storing Disk Images With ZFS

How to Create a Disk Image Using a ZFS Volume

How to Create a Disk Image Using a ZFS File

How to Export the ZFS Volume

How to Export the ZFS File

How to Assign the ZFS Volume or File to a Guest Domain

Creating a Snapshot of a Disk Image

How to Create a Snapshot of a Disk Image

Using Clone to Provision a New Domain

Cloning a Boot Disk Image

Using Volume Managers in a Logical Domains Environment

Using Virtual Disks on Top of Volume Managers

Using Virtual Disks on Top of Solaris Volume Manager

Using Virtual Disks When VxVM Is Installed

Using Volume Managers on Top of Virtual Disks

Using ZFS on Top of Virtual Disks

Using Solaris Volume Manager on Top of Virtual Disks

Using VxVM on Top of Virtual Disks

8.  Using Virtual Networks

9.  Migrating Domains

10.  Managing Resources

11.  Managing Domain Configurations

12.  Performing Other Administration Tasks

Part II Optional Oracle VM Server for SPARC Software

13.  Oracle VM Server for SPARC Physical-to-Virtual Conversion Tool

14.  Oracle VM Server for SPARC Configuration Assistant (Oracle Solaris 10)

15.  Using the Oracle VM Server for SPARC Management Information Base Software

16.  Logical Domains Manager Discovery

17.  Using the XML Interface With the Logical Domains Manager

Glossary

Index

Configuring Virtual Disk Multipathing

Virtual disk multipathing enables you to configure a virtual disk on a guest domain to access its back-end storage by more than one path. The paths lead through different service domains that provide access to the same back-end storage, such as a disk LUN. This feature enables a virtual disk in a guest domain to remain accessible even if one of the service domains goes down. For example, you might set up a virtual disk multipathing configuration to access a file on a network file system (NFS) server. Or, you can use this configuration to access a LUN from shared storage that is connected to more than one service domain. So, when the guest domain accesses the virtual disk, the virtual disk driver goes through one of the service domains to access the back-end storage. If the virtual disk driver cannot connect to the service domain, the virtual disk attempts to reach the back-end storage through a different service domain.


Note - Starting with the Oracle VM Server for SPARC 2.0 release, the virtual disk multipathing feature can detect when the service domain cannot access the back-end storage. In such an instance, the virtual disk driver attempts to access the back-end storage by another path.


To enable virtual disk multipathing, you must export a virtual disk back end from each service domain and add the virtual disk to the same multipathing group (mpgroup). The mpgroup is identified by a name and is configured when you export the virtual disk back end.

The following figure shows a virtual disk multipathing configuration, which is used as an example in the procedure How to Configure Virtual Disk Multipathing. In this example, a multipathing group named foo is used to create a virtual disk, whose back end is accessible from two service domains: primary and alternate.

Figure 7-2 Configuring Virtual Disk Multipathing

image:Shows how multipathing group, foo, is used to create a virtual disk, whose back end is accessible from two service domains: primary and alternative.

Virtual Disk Multipathing and Virtual Disk Timeout

With virtual disk multipathing, the path that is used to access the back end automatically changes if the back end becomes inaccessible by means of the currently active path. This path change occurs independently of the value of the virtual disk timeout property.

The virtual disk timeout property specifies the amount of time after which an I/O fails when no service domain is available to process the I/O. This timeout applies to all virtual disks, even those that use virtual disk multipathing.

As a consequence, setting a virtual disk timeout when virtual disk multipathing is configured can prevent multipathing from working correctly. This is especially the case with a small timeout value. So, it is best not to set a virtual disk timeout for virtual disks that are part of a multipathing group.

For more information, see Virtual Disk Timeout.

How to Configure Virtual Disk Multipathing

  1. Export the virtual disk back end from the primary service domain.
    # ldm add-vdsdev mpgroup=foo backend-path1 volume@primary-vds0

    where backend-path1 is the path to the virtual disk back end from the primary domain.

  2. Export the same virtual disk back end from the alternate service domain.
    # ldm add-vdsdev mpgroup=foo backend-path2 volume@alternate-vds0

    where backend-path2 is the path to the virtual disk back end from the alternate domain.


    Note - backend-path1 and backend-path2 are paths to the same virtual disk back end, but from two different domains (primary and alternate). These paths might be the same or different, depending on the configuration of the primary and alternate domains. The volume name is a user choice. It might be the same or different for both commands.


  3. Export the virtual disk to the guest domain.
    # ldm add-vdisk disk-name volume@primary-vds0 ldom

    Note - Although the virtual disk back end is exported several times through different service domains, you assign only one virtual disk to the guest domain and associate it with the virtual disk back end through any of the service domains.


Result of Virtual Disk Multipathing

After you configure the virtual disk with multipathing and start the guest domain, the virtual disk accesses its back end through the service domain it has been associated with (the primary domain in this example). If this service domain becomes unavailable, the virtual disk attempts to access its back end through another service domain that is part of the same multipathing group.


Caution

Caution - When defining a multipathing group (mpgroup), ensure that the virtual disk back ends that are part of the same mpgroup are effectively the same virtual disk back end. If you add different back ends into the same mpgroup, you might see some unexpected behavior, and you can potentially lose or corrupt data stored on the back ends.