LVM Version 2.0 Volume Groups in HP-UX 11i v3 (September 2008)
However, system memory is different. When this volume group is created or activated, the memory allocated is
based on the extents allocated to logical volumes and not on the maximum size of the volume group. This is
different from 1.0 version volume groups, in that LVM also allocates memory to match the provisioning on disk.
In other words, the system memory used by a 2.x volume group depends on how much of the volume group is
used. A volume group generously provisioned uses little memory as long as not many extents are allocated to
logical volumes. The memory usage grows roughly in proportion to the extents allocated to logical volumes.
As a consequence, the user can provision for very large volume groups without wasting system memory.
Metadata size on disk versus maximum volume group size
Figure 1 illustrates how much space is reserved on disk based on extent size and maximum volume group size.
Figure 1
Notes:
• All lines stop at 518 MB on the Y axis because of the limit of 32 million extents per volume group.
What are the Advantages of Over Provisioning with 2.x?
Over provisioning does not increase the memory footprint of the volume group. Over provisioning guarantees you
can grow the volume group up to its maximum size without having to create a second bigger volume group and
copy the data over.
17