IBM SG24-5131-00 User Manual
164
IBM Certification Study Guide AIX HACMP
When changing shared LVM components manually, you will usually need to
run through the following procedure:
run through the following procedure:
1. Stop HACMP on the node owning the shared volume group (sometimes a
stop of the applications using the shared volume group may be sufficient).
2. Make the necessary changes to the shared LVM components.
3. Unmount all the file systems of the shared volume group.
4. Varyoff the shared volume group.
5. Export the old volume group definitions on the next node.
6. Import the volume group from one of its disks on the next node. Make sure
you use the same VG major number.
7. Change the volume group to not auto-varyon at system boot time.
8. Mount all the file systems of the shared volume group.
9. Test the file systems.
10.Unmount the file systems of the shared volume group.
11.Varyoff the shared volume group.
12.Repeat steps 6 through 11 for all the other nodes with an old ODM of the
shared volume group.
13.Start HACMP again on the node usually owning the shared volume group.
8.4.2 Lazy Update
For LVM components under the control of HACMP for AIX, you do not have to
explicitly export and import to bring the other cluster nodes up-to-date.
Instead, HACMP for AIX can perform the export and import when it activates
the volume group during a failover. In a cluster, HACMP controls when
volume groups are activated. HACMP for AIX implements a function, called
Lazy Update, by keeping a copy of the timestamp from the volume group’s
VGDA. AIX updates this timestamp whenever the LVM component is
modified. When another cluster node attempts to vary on the volume group,
HACMP for AIX compares its copy of the timestamp (kept in the
/usr/sbin/cluster/etc/vg file) with the timestamp in the VGDA on the disk. If the
values are different, the HACMP for AIX software exports and re-imports the
volume group before activating it. If the timestamps are the same, HACMP for
AIX activates the volume group without exporting and re-importing.
explicitly export and import to bring the other cluster nodes up-to-date.
Instead, HACMP for AIX can perform the export and import when it activates
the volume group during a failover. In a cluster, HACMP controls when
volume groups are activated. HACMP for AIX implements a function, called
Lazy Update, by keeping a copy of the timestamp from the volume group’s
VGDA. AIX updates this timestamp whenever the LVM component is
modified. When another cluster node attempts to vary on the volume group,
HACMP for AIX compares its copy of the timestamp (kept in the
/usr/sbin/cluster/etc/vg file) with the timestamp in the VGDA on the disk. If the
values are different, the HACMP for AIX software exports and re-imports the
volume group before activating it. If the timestamps are the same, HACMP for
AIX activates the volume group without exporting and re-importing.
The time needed for takeover expands by a few minutes if a Lazy Update
occurs. A Lazy Update is always performed the first time a takeover occurs in
order to create the timestamp file on the takeover node.
occurs. A Lazy Update is always performed the first time a takeover occurs in
order to create the timestamp file on the takeover node.