Use the following command, where s partition_size sets the number of megabytes (MB) in each physical partition where the partition_size is expressed in units of MB from one through 1,024. (It's one through 131,072 for AIX 5.3.)

mkvg -y name_of_volume_group -s partition_size list_of_hard_disks

The partition_size variable must be equal to a power of two (for example: one, two, four or eight). The default value for standard and big volume groups is the lowest value to remain within the limitation of 1,016 physical partitions per physical volume. The default value for scalable volume groups is the lowest value to accommodate 2,040 physical partitions per physical volume.