SLVM Online Volume Reconfiguration (September 2009)

Abstract
SLVM (Shared Logical Volume Manager) is a mechanism that permits multiple systems in an HP
Serviceguard cluster to share (read/write) disk resources in the form of volume groups.
Starting with the HP-UX 11i v3 September 2009 release, you can change the configuration of a
shared volume group while it stays activated on all the nodes. There is no need to deactivate the
volume group on some nodes. This method is called Multi Node Online Reconfiguration (MORE). This
method is only available on Version 2.1 volume groups.
Alternatively, you can still use the Single Node Online Reconfiguration (SNOR) method that was
available prior to the HP-UX 11i v3 September 2009 release. This feature works on all volume group
versions. However, it requires the deactivation of the volume group on all but one node in a cluster.
This white paper describes both methods.
Multi Node Online Reconfiguration
Multi Node Online Reconfiguration (MORE) is introduced in the HP-UX 11i v3 September 2009
release. This feature enables you to change the configuration of LVM Version 2.1 volume groups
while the volume groups are activated in shared mode on any number of cluster nodes. Applications
can continue to use these volume groups without interruption while the volume groups are
reconfigured.
Prerequisites
In addition to the configuration necessary to share a volume group, online reconfiguration requires
the service of an LVM daemon, lvmpud. There is a maximum of one instance of this daemon running
at any time on the system. This daemon is not started by default.
A startup script (/sbin/init.d/lvm) is delivered as part of the HP-UX 11i v3 September 2009
release to start and stop the daemon. A configuration file (/etc/rc.config.d/lvmconf) is
provided to configure automatic startup.
To have lvmpud started automatically at each boot, include the following line in the
/etc/rc.config.d/lvmconf file:
START_LVMPUD=1
To stop the daemon, manually use the following command:
/sbin/init.d/lvm stop
To start again the daemon, manually use the command:
/sbin/init.d/lvm start
To start the lvmpud daemon even if START_LVMPUD is not set to 1, enter:
lvmpud
LVM Command Changes
The LVM CLI is not changed. There are no new options or new commands for MORE.
The only difference is that commands that were failing with the The volume group vg name is
active in Shared Mode. Cannot perform configuration change. message are now
configuring the volume group (Version 2.1 or higher volume groups only).