Building Disaster Recovery Serviceguard Solutions Using Metrocluster with EMC SRDF

E Configuring Oracle RAC in SADTA
Overview of Metrocluster for RAC
The Oracle RAC database can be deployed in a Metrocluster environment for disaster recovery
using SADTA. This configuration is referred to as Metrocluster for RAC. In this architecture, a
disaster tolerant RAC database is configured as two RAC databases that are replicas of each
other; one at each site of the Metrocluster. At any given time in a Metrocluster, the RAC database
at only one site is up and actively services clients while the other RAC database, which is a replica
on the remote site, remains passive. The active RAC database data I/O is continuously replicated
(synchronously or asynchronously) to the remote site using EMC SRDF.
When the active RAC database fails, or when the site hosting the active RAC database is lost in
a disaster, Metrocluster automatically initiates a site failover for the RAC database. A Metrocluster
site failover activates the passive database configuration at the remote site by starting it using the
replicated data in that site. After a successful site failover, the redundant RAC passive database
becomes the new active RAC database.
While configuring replicas of the RAC databases within a Metrocluster, the two sites in the
Serviceguard cluster must be configured by grouping cluster nodes based on the sites they are
located in. If you have CVM or CFS configured in your environment, create an SGeRAC-enabled
Oracle Clusterware sub-cluster and a Serviceguard Storage Management Suite CFS sub-cluster at
each site. Only nodes within a Serviceguard site can be members of these clusters.
For every site aware disaster tolerant RAC database, a RAC database must be configured at each
site using the Oracle Clusterware sub-cluster of the site.An Oracle Clusterware sub-cluster at one
site can be started and stopped independently of the Oracle Clusterware sub-cluster on the other
site.
In SADTA, CFS or CVM software can be used to form sub-clusters at each site. The Serviceguard
Storage Management Suite (SG SMS) Cluster File System (CFS) is layered above the Serviceguard
membership. The Cluster File System (CFS) sub-cluster is formed with membership from the cluster
nodes in a site as defined in the underlying cluster.
The CFS sub-cluster at a site manages the disks connected to the nodes in that site. In SADTA, a
CFS sub-cluster is present at each site. The CFS sub-clusters at each site have their own namespaces.
As a result, the same Cluster Volume Manager (CVM) disk group name can be used in both of the
sites in a Metrocluster. While the same CVM disk group and CFS filesystem name can be used in
both subcluster, the disk group package name and the mountpoint package name need to be
unique across both subclusters. The database at each site uses the CFS sub-cluster file systems
created over the local disk of a replicated disk pair.
The RAC database processes the disk groups, and file systems at each site are configured in a
stack of inter-dependent MNP packages. The RAC database processes are packaged using the
SGeRAC Toolkit (delivered as part of the SGeRAC product). The CVM DG MNP and CFS MP MNP
packages are created using SG SMS commands for the disk groups and cluster file systems that
are used to store the database.
For more information about using SG SMS commands to create disk groups and cluster file systems,
see the documents available at http://www.hp.com/go/hpux-serviceguard-docs ->HP Serviceguard
Storage Management Suite <version>. Also, see the Serviceguard, SGeRAC, and SMS Compatibility
and Feature Matrix and the latest release notes for your version of Serviceguard for up-to-date
information about support for CVM and CFS, available at: http://www.hp.com/go/
hpux-serviceguard-docs.
For SADTA, a Site Controller Package must be configured to provide robust site failover semantics
for a site aware disaster tolerant RAC database. The Site Controller Package starts the configured
local RAC MNP stack packages on the site where it is started. The Site Controller Package monitors
the RAC MNP stack packages. When these packages fail, the Site Controller Package fails over
to the remote site. As part of its startup on the remote site node during failover, the Site Controller
Package prepares the replicated data storage and runs the passive RAC MNP stack packages in
the remote site ensuring disaster recovery for the database.
98 Configuring Oracle RAC in SADTA