Volume groups

Find information about volume groups.

A volume group is a collection of one or more physical volumes of varying sizes and types. A physical volume can belong to only one volume group per system. There can be up to 4096 active volume groups on the Virtual I/O Server.

When a physical volume is assigned to a volume group, the physical blocks of storage media on it are organized into physical partitions of a size determined by the system when you create the volume group. For more information, see Physical Partitions.

When you install the Virtual I/O Server, the root volume group called rootvg is automatically created that contains the base set of logical volumes required to start the system logical partition. The rootvg includes paging space, the journal log, boot data, and dump storage, each in its own separate logical volume. The rootvg has attributes that differ from user-defined volume groups. For example, the rootvg cannot be imported or exported. When using a command or procedure on the rootvg, you must be familiar with its unique characteristics.

Small systems might require only one volume group to contain all of the physical volumes (beyond the rootvg volume group). You can create separate volume groups to make maintenance easier because groups other than the one being serviced can remain active. Because the rootvg must always be online, it contains only the minimum number of physical volumes necessary for system operation. It is recommended that the rootvg not be used for client data.

You can move data from one physical volume to other physical volumes in the same volume group by using the migratepv command. This command allows you to free a physical volume so it can be removed from the volume group. For example, you could move data from a physical volume that is to be replaced.