High Availability for Oracle ASM using HP Serviceguard Solutions, September 2010

7
HP Serviceguard support for ASM on HP-UX 11i v3 and
later
This document describes how to configure Oracle ASM database with HP Serviceguard for high
availability using the Oracle database Toolkit in Serviceguard ECMT. Look at the Serviceguard ECMT
support matrix available at
http://www.hp.com/go/hp HP Enterprise Cluster
Master Toolkit for the supported versions of Serviceguard ECMT, Serviceguard and Oracle.
ux-serviceguard-docs
Note that for database failover, each database should store its data in its own disk group. Refer to
Oracle documentation for limitation imposed by ASM on the number of disk groups. The disk group
members must be logical volumes managed by HP Logical Volume Manager (LVM). Initial release of
HP-UX 11i v3 did not support LVM version 2. With HP-UX 11i v3 0803, LVM version 2 logical
volumes are also supported as members of the ASM disk groups.
A new I/O infrastructure that enables the native built-in multipathing functionality is introduced in
HPUX 11i v3. This feature offers users a continuous I/O access to a LUN or disk if any of the paths
fails. This feature is enabled in the operating system by default. In addition, new DSF (device special
file) format is introduced in this operating system known as persistent DSF. An example of persistent
DSF is /dev/disk/disk1, compared to the legacy DSF, /dev/rdsk/cxtydz.
A new cluster wide DSF format is introduced in HP-UX 11i v3 known as cDSF. HP Serviceguard
A.11.20 requires the Serviceguard patch PHSS_41225 to support this feature. An example of cDSF is
/dev/cdisk/disk1, compared to the persistent DSF, /dev/disk/disk1. ASM cannot detect cDSF format
and hence this format cannot be used to create the ASM disk groups.
It is the responsibility of Serviceguard to provide the necessary I/O fencing when failover is provided
for a single instance Oracle database instance. Serviceguard provides I/O fencing for a failover
package via a feature in the volume manager: exclusive activation of volume groups. Hence it is
required that the ASM disk group members be LVM logical volumes.
The sample command sequence for configuring LVM logical volumes for use by ASM can be found in
the Appendix.
Framework for ASM support with Serviceguard
The framework for ASM integration with Serviceguard makes use of a Multi-Node Package (MNP) to
encapsulate the per-node ASM instances, with one or more Oracle single instance failover packages
dependent on this MNP. This configuration enables the database instance to start up in the right order
in relation to the ASM instance, and in the event of failover, to relocate to a node where an ASM
instance is available. The benefits of this package framework for single instance Oracle database
using ASM-based storage are:
• Avoid failing over ASM instance. This reduces the failover time due to ASM instance restart.
• Many database instances can share one ASM instance per node.
• Sequencing between Oracle database instance and ASM instance during
startup/shutdown/failover.
• Flexibility of the database instances to fail over independently.
HP provides a bundle of Toolkit scripts known as HP Serviceguard Enterprise Cluster Master Toolkit
(ECMT) which provides for the integration of ASM with Serviceguard. The operation of the Toolkit is
described below.