Federated storage is the collection of autonomous storage resources governed by a common management system that provides rules about how data is stored, managed, and migrated throughout the storage network. In this definition, storage resources include disk capacity managed by controllers or appliances controlling multiple arrays.
Practitioners should think of individual resources (e.g. arrays) as nodes within the federation. By enabling a loosely coupled set of storage resource nodes to act unilaterally and still be managed centrally, organizations can, over some distance, create networks of virtually limitless capacities, move data and applications globally, eliminate disruptive migrations and dramatically improve recovery.
Technologies are coming onto the market to exploit such architectures, particularly in file and object environments (e.g. scale out NAS, Google File System, DDN's WOS, etc). These include scale out NAS and object-based file systems. In block-based worlds, as is often the case, functional and robust software lags hardware.
UPDATE: On March 11, 2010, EMC announced a vision of federated storage based on Yotta Yotta technology that is purportedly block-based federated storage. At EMC World 2010, EMC announced VPLEX, a federated storage architecture for block-based systems.
Action Item: By late 2012, federated storage will be the architecture of choice for large new storage deployments. These capabilities will dramatically improve IT's ability to respond to business needs with minimal disruptions. IT organizations should plan to aggressively adopt federated storage as it becomes commercially available.