An Oracle Extended Cluster consists of nodes that are located in multiple locations called sites.
When you deploy an Oracle Standalone Cluster, you can also choose to configure the cluster as an Oracle Extended Cluster. You can extend an Oracle RAC cluster across two, or more, geographically separate sites, each equipped with its own storage. In the event that one of the sites fails, the other site acts as an active standby.
Both Oracle ASM and the Oracle Database stack, in general, are designed to use enterprise-class shared storage in a data center. Fibre Channel technology, however, enables you to distribute compute and storage resources across two or more data centers, and connect them through Ethernet cables and Fibre Channel, for compute and storage needs, respectively.
You can configure an Oracle Extended Cluster when you install Oracle Grid Infrastructure. You can also do so post installation using the
ConvertToExtended script. You manage your Oracle Extended Cluster using CRSCTL.
Oracle recommends that you deploy Oracle Extended Clusters with normal redundancy disk groups. You can assign nodes and failure groups to sites. Sites contain failure groups, and failure groups contain disks. For normal redundancy disk groups, a disk group provides one level of failure protection, and can tolerate the failure of either a site or a failure group.
The following conditions apply when you select redundancy levels for Oracle Extended Clusters:
Table 9-1 Oracle ASM Disk Group Redundancy Levels for Oracle Extended Clusters
|Redundancy Level||Number of OCR and Voting Files Disk Groups||Number of OCR Backup and GIMR Disk Groups|
|Normal redundancy||1 failure group per data site, 1 quorum failure group||1 failure group per data site|
|Flex redundancy||1 failure group per data site, 1 quorum failure group||Three failure groups, with 1 failure group per site|
|High redundancy||Not supported||Three failure groups, with 1 failure group per site|