Logical volumes

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A logical volume is a set of logical partitions that AIX® makes available as a single storage unit, that is, the logical view of a disk.

A logical partition is the logical view of a physical partition. Logical partitions can be mapped to one, two, or three physical partitions to implement mirroring.

In the PowerHA® SystemMirror® environment, logical volumes can be used to support a journaled file system or a raw device.

Specify the superstrict disk allocation policy for the logical volumes in volume groups for which forced varyon is specified. Using this configuration allows for the following properties:

  • Guarantees that copies of a logical volume always reside on separate disks
  • Increases the chances that forced varyon will be successful after a failure of one or more disks.

If you plan to use forced varyon for the logical volume, apply the superstrict disk allocation policy for disk enclosures in the cluster.

To specify the superstrict disk allocation policy, complete the following steps:

  1. From the command line, enter smit cl_admin.
  2. In SMIT, select Storage > Logical Volumes and select Add a Logical Volume or Change a Logical Volume.
  3. Select Allocate each logical partition copy on a separate physical volume.
  4. When using the superstrict disk allocation policy, specify the correct number of physical volumes for this logical volume. Do not use the default setting of 32 physical volumes.