Horizontal scaling for OracleThis is called "horizontal scaling", or the "scale out" approach, whereby small server blades are genned-in to an Oracle RAC cluster over a high-speed interconnect. Horizontal scaling requires Real Application Clusters and also provides the benefit of guaranteed continuous availability.
Vertical scaling for OracleWe also see the "scale up" approach (the vertically scalable architecture) whereby server resources (CPU, RAM, Disk) can be added into a single, monolithic server. Examples include the HP Superdome (64 CPU), the Unisys ES7000 (32 Processors) The Sun Sun Fire and the IBM X Series.
Vertical scaling has several benefits over horizontal scaling for Oracle databases:
- RAC is not required
- Machine resources (especially CPU) are instantly available for sharing
- A single-server requires less overhead and management