AIX Version 4.3 Differences Guide

extended to 511 logical volumes and 128 physical volumes by specifying the -B
flag.
5.6.3 Small VG to Big VG Conversion
To convert the small VG to a big VG, a number of free physical partitions are
needed to expand the VGDA/VGSA. Depending on the size of the physical
partition and the current size of the VGDA, the number of partitions required are
calculated. Since the first partition starts immediately after the end of the
secondary VGDA, if it is occupied by a logical partition, it will be migrated to
another free physical partition on the disk. This first physical partition will then be
removed from the list of available partitions (not be moved or allocated for any
reason), and the remaining partitions will be renumbered. After the conversion,
the total number of physical partitions on the disk will not change, except that the
extra partitions allocated for the VGDA are marked non allocatable.
You should be aware of the following items when you perform a conversion from
a small VG to a big VG:
• All the disks in the volume group should have enough free PPs for the
conversion to be possible.
• All the logical volumes in the volume group must be in closed/synced state.
• All physical volumes must be available and be in the ACTIVE state.
• The volume group is varied on in management mode to prevent opening of
any logical volumes.
• The ownership/permissions of special device files will only be preserved if mklv
or chlv are used with the -U, -G, or -P flags.
Currently, the migratepv command does not allow the migration of individual
physical partitions. The conversion needs to free up just enough physical
partitions from the beginning of the disk to elsewhere. The current
implementation will try to migrate the partitions within the physical volume, and
the user must move the partitions to other disks in the volume group.
5.6.4 Big VG Limitations
The following list are the limitations of a big VG:
• A big VG is not enabled for concurrent access. This is posed by the
communication path used by the concurrent logical volumes. It will be
prohibitively slower for the big VG to communicate across nodes due to an
increase in the number of disks.
• The rootvg cannot be converted to the big VG format.
• A big VG cannot be imported or activated on pre-AIX 4.3.2 levels.
5.7 Concurrent Online Mirror Backup and Special File Support (4.3.2)
AIX 4.3.1 provided support for an on-line backup mechanism for a mirrored raw
logical volume. But it lacked support for file system access and restricts
concurrent mode access for the volume group.
AIX 4.3.2 enhances the capabilities of the online backup in AIX 4.3 to support:
92 AIX Version 4.3 Differences Guide