Database Reference
In-Depth Information
Flex Cluster to Increase Scalability
Oracle RAC 12c introduces Oracle Flex Cluster to improve cluster scalability. Before Oracle 12c, all the nodes of an
Oracle RAC cluster were tightly coupled. This architecture is difficult to scale and manage as the number of nodes
in the cluster increases beyond a certain level. One of the issues with this architecture is the number of interconnect
links between the cluster nodes. In this architecture, each node is connected to every other node in the cluster. For an
N-node cluster, the number of interconnect links is N *(N-1)/2; for a 100-node cluster, this number reaches 4,950. The
Oracle 12c Flex Cluster reduces the number of network links between nodes by allowing loosely coupled Leaf Nodes
and requiring a tightly coupled cluster only among a smaller number of Hub Nodes. In this Flex Cluster architecture,
the Leaf Nodes connect only to the Hub Nodes that they are attached to, and there is no interconnect among the Leaf
Nodes. This architecture significantly reduces the number of connections among the cluster nodes and makes the
cluster more scalable and manageable.
Consolidating Database Services with Oracle RAC
In the traditional corporate computing model, one infrastructure is usually built for one application, with little or
no resource sharing among applications. Not only does this model result in low efficiency and poor utilization of
resources, it also makes it very difficult to reassign resources to adapt to the rapid pace of business change. Many
systems have to preallocate large amounts of system resources in their capacity planning to cover peak demand and
future growth. Today's IT departments, under increasing pressure to provide low-cost, flexible computing services,
have to adapt to the idea that multiple applications services can be consolidated to share a pool of the computing
resources: servers, networks, and storage. Grid computing originated from the concept of the electricity utility grid,
and the recent Private Cloud is also based on this idea. These models have the following characteristics:
1.
Consolidation: Many applications with different workloads are consolidated in the same
infrastructure.
2.
Dynamic resource sharing: All resources in the infrastructure are shared and can be
dynamically reassigned or redistributed to applications services as needed.
3.
High Availability: Applications within the shared infrastructure can be failed over or
migrated across physical resources. This provides a virtualized infrastructure service that
is independent of the physical hardware and also protects applications against unplanned
system outages and planned system maintenance.
4.
Scalability: Allows adding more physical resources to scale the infrastructure.
Consolidation and resource sharing dramatically increase resource utilization, and reduce hardware and system
costs. There are cost savings both in capital expenses and operating expenses, as you not only need to purchase
less hardware and software, but you can spend less on management and ongoing support costs. Consolidation and
resource sharing also confer the benefits of high availability, flexibility, and scalability on application services.
Oracle RAC, along with Oracle Clusterware and ASM, provides the key technologies to implement this shared
resource infrastructure for database consolidation.
Oracle Clusterware and ASM provide infrastructure which consists of a pool of servers, along
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with storage and a network for database consolidation.
Oracle Clusterware and RAC provide high availability and scalability for all databases that
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share this infrastructure.
Oracle RAC features such as Instance Caging, Database Resource Manager, and Quality of
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Service enable the efficient use of shared resources by databases.
The enhancement introduced by Oracle 12c Clusterware, like the policy-based approach
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for Clusterware management, allows for dynamic resource reallocation and prioritization of
various applications' workloads consolidated in the shared cluster infrastructure.
