VxVM Software Disks

When a physical disk is brought under VxVM software control, it is either initialized or encapsulated.

Initialized Disks

Initialized disks are reformatted with either one or two partitions, and all data is destroyed. The partitions are used to store the VxVM software configuration and data areas called private and public regions.

The private region is a small partition where disk group configuration information is stored. The private region has the following characteristics:

  • It is usually slice 3.
  • Region size starts at 1024 sectors in early versions of the VxVM software, and 2048 sectors in version 3.2. Use the vxdisksetup command privlen option to expand the size of the private region. This is a complicated procedure and is not recommended. The procedure for expanding the private region is addressed in a lab exercise.
  • It is assigned vtoc tag number 15 for identification purposes.
  • This region is not used for data storage.
  • The private region contains the following information:
  • Disk name and indentifier
  • Disk group name and identifier
  • Disk group configuration copy

The public region uses the remaining space available on the physical disk to store subdisks. The public region has the following characteristics:

  • It is usually slice 4.
  • It is used for data storage.
  • The region is maintained by the VxVM software commands.
  • It is assigned vtoc tag number 14 for identification purposes.

Initialized disks can be configured in one of three methods:

  • The sliced configuration – Public and private regions are defined as separate Solaris OE partitions. This is the preferred method for initializing a VxVM software disk.
  • The simple configuration – Public and private regions are defined as a single Solaris OE partition.

These are volatile devices and disappear after a reboot if they are not in use or defined in the /etc/vx/volboot file.

  • The nopriv configuration – The disk is configured without a private region. Configuration information is held and maintained by a sliced disk acting as a proxy.

These disks are not automatically discovered at bootup unless  defined in the /etc/vx/volboot file.

Encapsulated Disks

Encapsulation brings a physical disk under the VxVM software control  and preserves the data. The /etc/vfstab file is modified to reflect the new volume names on the disk’s file systems. Encapsulation has the following characteristics:

  • The /etc/vfstab file requires free space on the disk, usually in the private region, to store configuration information.
  • The file size starts at 1024 sectors to the VxVM software version 3.2, and 2048 sectors in version 3.2 and later.
  • Encapsulation fails if there is not enough free space to build a private region. If space is not available for a private region, use the nopriv option.
  • All partitions on the disk are reassigned to a new public region, which is usually slice 6.
  • Boot disk can be encapsulated and remain bootable.

Note – Avoid nopriv configurations. Support for this configuration is  being phased out. Encapsulation, including boot disk encapsulation, is covered later in this course.

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