Logical volumes

After you create a volume group, you can create logical volumes within that volume group.

A logical volume, although it can reside on noncontiguous physical partitions or even on more than one physical volume, appears to users and applications as a single, contiguous, extensible disk volume. You can create additional logical volumes with the mklv command. This command allows you to specify the name of the logical volume and define its characteristics, including the number and location of logical partitions to allocate for it.

After you create a logical volume, you can change its name and characteristics with the chlv command, and you can increase the number of logical partitions allocated to it with the extendlv command. The default maximum size for a logical volume at creation is 512 logical partitions, unless specified to be larger. The chlv command is used to override this limitation.

Note: After you create a logical volume, the characteristic LV STATE, which can be seen using the lslv command, is closed. It becomes open when, for example, a file system has been created in the logical volume and the logical volume is mounted.

Logical volumes can also be copied with the cplv command, listed with the lslv command, removed with the rmlv command, and have the number of copies they maintain increased or decreased with the mklvcopy and the rmlvcopy commands, respectively. Logical Volumes can also be relocated when the volume group is reorganized.

The system allows you to define up to 255 logical volumes per standard volume group (511 for a big volume group and 4095 for a scalable volume group), but the actual number you can define depends on the total amount of physical storage defined for that volume group and the size of the logical volumes you define.