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88 IBM Certification Study Guide AIX HACMP
3.4.4.4 Varying Off the Volume Group on the Destination Nodes
Use the
varyoffvg command to deactivate the shared volume group so that it
can be imported onto another destination node or activated as appropriate by
the cluster event scripts. Enter:
varyoffvg volume_group_name.
3.4.5 Quorum
Quorum is a feature of the AIX LVM that determines whether or not a volume
group can be placed online using the
varyonvg command, and whether or not
it can remain online after a failure of one or more of the physical volumes in
the volume group.
Each physical volume in a volume group has a Volume Group Descriptor
Area (VGDA) and a Volume Group Status Area (VGSA).
VGDA Describes the physical volumes (PVs) and logical volumes (LVs)
that make up a volume group and maps logical partitions to
physical partitions. The
varyonvg command reads information from
this area.
VGSA Maintains the status of all physical volumes and physical partitions
in the volume group. It stores information regarding whether a
physical partition is potentially inconsistent (stale) with mirror
copies on other physical partitions, or is consistent or
synchronized with its mirror copies. Proper functioning of LVM
mirroring relies upon the availability and accuracy of the VGSA
data.
3.4.5.1 Quorum at Vary On
When a volume group is brought online using the
varyonvg command, VGDA
and VGSA data structures are examined. If more than half of the copies are
readable and identical in content, quorum is achieved and the
varyonvg
A QUORUM of disks required to
keep the volume group online?
This field is site-dependent. See 3.4.5, “Quorum” on
page 88 for a discussion of quorum in an HACMP
cluster.
Options Description
This section does not apply to the IBM 7135-110 or 7135-210 RAIDiant
Disk Array, which provides its own data redundancy.
Note