IBM AIX HACMP SG24-5131-00, Hardware User Manual

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Cluster Management and Administration
163
8.4 Changing Shared LVM Components
Changes to VG constructs are probably the most frequent kind of changes to
be performed in a cluster. As a system administrator of an HACMP for AIX
cluster, you may be called upon to perform any of the following LVM-related
tasks:
• Creating a new shared volume group
• Extending, reducing, changing, or removing an existing volume group
• Importing, mirroring, unmirroring, or synchronizing mirrors of a volume
group
• Creating a new shared logical volume
• Extending, reducing, changing, copying, or removing an existing logical
volume (or a copy)
• Creating a new shared file system
• Extending, changing, or removing an existing file system
The varyon of a shared volume group will only succeed if the information
stored in the VGDA on the disks of the shared volume group and the
information stored in the ODM are equal. After changes in the volume group
(e. g. increasing the size of a file system), the information about the volume
group in ODM and in the VGDA on the disks are still equal, but it will be
different from the information in the ODM of a node that did not have the
volume group varied on at the time of the change. In order to keep a takeover
from failing, the volume group information must be synchronized. There are
four distinct ways to keep all the volume group ODMs synchronized:
• Manual Update
• Lazy Update
• C-SPOC
• TaskGuide
Chapters 4 and 5 of the
HACMP for AIX, Version 4.3: Administration Guide
,
SC23-4279, describe in detail how to change shared LVM components.
8.4.1 Manual Update
Sometimes, manual updates of shared LVM components are inevitable
because you cannot do some of the tasks mentioned above with any of the
tools. For example, neither with C-SPOC nor with TaskGuide or Lazy Update
is it possible to remove a VG on all of the cluster nodes.