Storage Virtualization is the newest of the three management technologies and is far and away the most efficient and reliable technology. In a storage virtualization implementation, a storage controller sits between a pool of centralized storage and the servers, which have storage needs. With virtualization, IT managers can share storage resources to all servers regardless of storage hardware type (direct attached SCSI and IDE storage can be shared, as well as large Fibre Channel RAID units) or physical location (Fibre Channel links can run 10km in length). The most common implementation uses a specialized server running storage virtualization software acting as the gateway between the storage and the servers (see diagram). Two solutions that worked well in our tests in house are FalconStors IPstor and DataCores SANsymphony virtualization software packages.Since the servers and storage are in different zones there is no danger of servers or users accidentally using and corrupting the data on the shared storage. On the server side, a specialized device driver, allowing the server to communicate with the storage controller, needs to be installed. Once the software and hardware is configured, the storage controller will be able to distribute LUNs out to the servers easily through a central management console. For mission-critical sites, its extremely important to set up redundant storage controllers, since an outage at the storage controller will cripple all of the servers than rely on the SAN. Since storage controllers are essentially acting like RAID controllers in a storage virtualization scenario, by beefing up a storage controller with RAM and additional processors, its possible to boost the overall performance of a SAN by doing some caching on the controllers.
To make storage virtualization work, the SAN is configured to have two zones: a zone for the servers and a second zone for the storage. To communicate to both sides, the storage controller (i.e. the server with the virtualization software) runs two Fibre Channel HBAs (one dedicated to each zone) and the software routes the traffic from one zone out to the other.