1.2.6 Storage Pools

Exascale uses pool disks and storage pools to organize the physical storage provided by Exadata storage servers.

An Exascale storage pool is a collection of pool disks that provides persistent physical storage for Exascale vaults and files.

A working Exascale cluster requires at least one storage pool. Note that there is no need to define multiple storage pools for data separation because Exascale vaults provide strong data isolation.

Each storage pool is a collection of pool disks with a common media type (for example, HC). You cannot define a storage pool with pool disks having a mixture of media types (for example, HC and XT). Currently, only one storage pool is permitted for each media type.

A storage pool can contain pool disks that reside on different generations of Exadata storage server hardware, which allows for easy migration to new generations of Exadata hardware.

You can dynamically reconfigure a storage pool by changing the size of the pool disks or by adding or removing pool disks (or Exadata storage servers). However, pay attention to the following:

• For each storage pool, use pool disks that are spread across all of the available storage devices in each storage server.

• On each storage server, maintain consistent sizing for all of the pool disks belonging to a storage pool. However, pool disks on different storage servers can have different sizes.

Because a storage pool may contain a vast amount of data, Exascale automatically organizes it using internal constructs to optimize performance, availability, and manageability.

Within each storage pool, Exascale groups pool disks and their associated storage servers into disk partner groups and cell partner groups. This organization maximizes availability by limiting the impact of multiple simultaneous failures. Separate groups enable the system to handle simultaneous failures independently, and failures that affect only a small group are statistically less likely than failures across the entire system.

Each storage pool also contains internal failure constructs called storage pool rings. Storage pool rings ensure that data with different content types and redundancy requirements use separate disk partner groups. Through the use of separate storage pool rings and native integration with Oracle Database, Exascale automatically isolates Oracle Database data files from recovery files. This organization guarantees that if multiple failures affect a data file, its corresponding recovery files remain available.

You cannot control the organization of storage pool rings or partner groups. However, Exascale provides information about these constructs to support system monitoring and to help users understand the impact of any storage failure scenario.