Describe principle~
The real application clusters database highly available and extensible.Failure of one node in the cluster does not affect customer usage until the last node in cluster fails.
Defects~
The high cost.Each node has a separate oracle license and also needs a rac license.
The high speed interconnection requirements make the nodes close together, which means that a natural disaster may destroy the whole cluster.
The heardware configuration：
For RAC database,include two or more nodes. Redundant power supply,network card,dual CPU and error correction memory.
Shared disks should also have built-in hardware redundancy -multiple power supplies,raid-enabled disks,and so on.
The software configuration:
Cluster Ready Service,CRS
The network configuration:
Each node in RAC has at least three IP addresses.
Public network:All normal connections between the node and the server.
Private network:Intra-cluster node communication.
Virtual IP:Listen for addresses,and support rapid connect-time failover.
Public and private networks are best bond,providing redundancy and bandwidth.
Summary:This blog birefly describes RAC.
NOTE:The next blog will describe the RAC process.
