Comparing Oracle Database Appliance and Exadata

Oracle Database Appliance (ODA) is in many ways similar to an Exadata quarter rack: they both use two similar compute servers in an engineered system configuration, with shared storage and flash storage. But in other ways, especially networking and storage, they differ significantly. In particular:

• Storage connectivity: ODA uses SAS direct attachment, while Exadata uses an InfiniBand backbone connected to dedicated storage servers
• Flash memory: Exadata has significantly more flash memory than ODA does. While both can store ASM diskgroups in flash, Exadata also has flash cache capability. ODA’s default configuration uses flash to store redo logs; this helps compensate for ODA’s lack of
  battery-backed disk write cache in the latency-sensitive redo write workload.
• Expandability: ODA currently comes in a single 2-server, 12TB configuration. An Exadata quarter-rack configuration has
  2 compute servers and a minimum of 21TB raw storage. Both compute capacity and storage are expandable virtually without limit, given sufficient number of racks and network backbone.

The chart below summarizes the similarities and differences: