Managing Serviceguard Eighteenth Edition, September 2010

About the Volume Monitor
Simply monitoring each physical disk in a Serviceguard cluster does not provide
adequate monitoring for volumes managed by Veritas Volume Manager from Symantec
(VxVM) or logical volumes managed by HP-UX Logical Volume Manager (LVM),
because a physical volume failure is not always a critical failure that triggers failover
(for example, the failure of a single physical disk within a mirrored volume is not
considered critical). For this reason, it can be very difficult to determine which physical
disks must be monitored to ensure that a storage volume is functioning properly. The
HP Serviceguard Volume Monitor provides a means for simple and effective monitoring
of storage volumes.
IMPORTANT: Check the latest version of the release notes (at the address given in the
preface to this manual) for information about Serviceguard support for the volume
monitor.
Using the Volume Monitor
NOTE: For LVM, using this monitor is an alternative to using Event Monitoring
Service (EMS) resource dependencies; see “Using EMS to Monitor Volume Groups”
(page 132). EMS does not currently provide a monitor for VxVM.
Configure the Volume Monitor as a service in a package that requires access to a VxVM
or LVM storage volume.
The package can be a failover package or multi-node package. For example, you can
configure the monitor as a service in a failover package to monitor a storage volume
(or multiple storage volumes) required by the package application. Alternatively, the
monitor could be used in a multi-node package to monitor identically-named root,
boot, or swap volumes on cluster nodes. Because the root, boot, and swap volumes are
critical to the functioning of the node , the service should be configured with
service_restart (page 301) set to yes.
When a monitored volume fails or becomes inaccessible, the monitor service will exit,
causing the package to fail on the current node. The package’s failure behavior depends
on its configured settings. For prompt recovery, HP recommends setting the value of
service_restart (page 301) for the monitoring service to none.
To ensure that a package requiring a storage volume does not attempt to start on or
fail over to a node where the storage volume is unavailable, the monitor service may
be configured in a separate package, and a package dependency may be used to ensure
that the required package is running, indicating the storage is available. Depending
on the configuration, the monitor package could be a multi-node or failover package,
and would be required to be running by the storage volume-dependent application
package. Alternatively, if you are using EMS, please be aware that EMS resource
172 Planning and Documenting an HA Cluster