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Using nopriv disks for encapsulation

Encapsulation converts existing partitions on a specified disk to volumes. If any partitions contain file systems, their /etc/fstab entries are modified so the file systems are mounted on volumes instead.

Disk encapsulation requires that enough free space be available on the disk (by default, 1 megabyte) for storing the private region that VxVM uses for disk identification and configuration information. This free space cannot be included in any other partitions.

See the vxencap(1M) manual page.

You can encapsulate a disk that does not have space available for the VxVM private region partition by using the vxdisk utility. This is done by configuring the disk as a nopriv devices that does not have a private region.

The drawback with using nopriv devices is that VxVM cannot track changes in the address or controller of the disk. Normally, VxVM uses identifying information stored in the private region on the physical disk to track changes in the location of a physical disk. Because nopriv devices do not have private regions and have no identifying information stored on the physical disk, tracking cannot occur.

One use of nopriv devices is to encapsulate a disk so that you can use VxVM to move data off the disk. When space has been made available on the disk, remove the nopriv device, and encapsulate the disk as a standard disk device.

A disk group cannot be formed entirely from nopriv devices. This is because nopriv devices do not provide space for storing disk group configuration information. Configuration information must be stored on at least one disk in the disk group.

Creating a nopriv disk for encapsulation
Warning: Do not use this procedure to encapsulate a root disk. Part of the swap area on a root disk can be used to form the private region.

 To create a nopriv disk for encapsulation

  1. If it does not exist already, set up a partition on the disk for the area that you want to access using VxVM.
  2. Use the following command to map a VM disk to the partition:

# vxdisk define partition-device type=nopriv

where partition-device is the basename of the device in the /dev directory. For example, to map partition 3 of disk device sdc, use the following command:

# vxdisk define sdc3 type=nopriv

Creating volumes for other partitions on a nopriv disk

 To create volumes for other partitions on a nopriv disk

  1. Add the partition to a disk group.
  2. Determine where the volume is to reside within the partition.
  3. If no data is to be preserved on the partition, use vxassist to create a volume with the required length.
    Warning: By default, vxassist re-initializes the data area of a volume that it creates. If there is data that needs to be preserved on the partition, do not use vxassist. Instead, create the volume with vxmake and start the volume with the command vxvol init active.