Understanding tiered storage
Tiered storage allows you to connect multiple diverse storage subsystems behind a single server (or cluster). Using tiered storage, you can match application storage requirements (in terms of performance and scaling) to your storage subsystems. This section describes the concept of tiered storage, and explains how to configure the storage server to work with your storage subsystems to create a tiered storage architecture.
Based on a storage subsystem's performance characteristics, it is classified as belonging to a certain tier, and each tier is used differently in the enterprise storage architecture. The currently supported storage subsystems fit into the tiered storage model as follows:
| Tier | Performance | Drive Type | RPM (if disk) |
| 0 | Extremely high | Flash or solid-state memory; not disk | N/A |
| 1 | Very high | SAS | 15,000 |
| 2 | High | SAS | 10,000 |
| 3 | Nearline | Nearline (NL) SAS | 7,200 |
| 4 | Archival | Nearline (NL) SAS | 7,200 |
| 5 | Long-term storage (Tape) | N/A (Tape) | N/A |
The NAS server supports tiers of storage, where each tier is made up of devices with different performance characteristics or technologies. The NAS server also supports storage virtualization through applicable Hitachi RAID arrays using HUVM.
Tiers of storage and storage virtualization are fully supported by Data Migrator, an optional feature which allows you to optimize the usage of tiered storage and remote NFSv3 servers. Note, however, that Data Migrator does not support migration to or from tape storage devices or tape library systems. For detailed information about Data Migrator, refer to the Data Migrator Administration Guide.