What is Oracle Exadata Storage Server?

Oracle Exadata Storage Server is a highly optimized storage server that runs Oracle Exadata System Software to store and access Oracle Database data. With traditional storage, data is transferred to the database server for processing. In contrast, Oracle Exadata System Software provides database-aware storage services, such as the ability to offload SQL and other database processing from the database server, while remaining transparent to the SQL processing and database applications. Oracle Exadata Database Machine storage servers process data at the storage level, and pass only what is needed to the database servers.

Oracle Exadata System Software enables cost-effective modular storage hardware to be used in a scale-out architecture while providing a high level of availability and reliability. All single points of failure are eliminated in the Oracle Exadata Storage Server architecture by data mirroring, fault isolation technology, and protection against disk and other storage hardware failure.

Storage in Oracle Exadata Database Machine consists of servers, cell disks, grid disks, Oracle ASM disk groups, and Oracle ASM failure groups.

The following image shows Oracle ASM disk groups created from Oracle Exadata Storage Server grid disks. It represents a typical, but simplified configuration, that can be used as a model for building larger storage grids with additional storage servers and disks.

Figure 1 : An Oracle Exadata Storage Server grid

The storage grid in Figure 1 illustrates the following:

  • The storage servers in the grid use an RDMA Network Fabric network to connect to the database servers that have a single-instance database or Oracle Real Application Clusters (Oracle RAC) database installation.

  • Each storage server contains multiple physical disks.

  • Each cell disk represents a physical disk and a LUN.

  • Each cell disk is partitioned into grid disks.

  • Oracle ASM disk groups are created using the grid disks.

Oracle ASM failure groups are created to ensure that files are not mirrored on the same storage server, enabling the system to tolerate the failure of a storage server. The number of failure groups equals the number of storage servers. Each failure group is composed of a subset of grid disks in the Oracle ASM disk group that belong to a single storage server.