The Merits of Storage Virtualization

Storage virtualization is an abstraction (separation) of logical storage from physical storage so that it may be accessed without regard to physical storage or technology management methods.

Storage virtualization makes possible the identification, provisioning and management of data storage at multiple locations. Storage virtualization can extract data from completely different applications as if they were a single, consolidated resource.

Managing disk storage was once simple. If we needed more space, we got a bigger disk drive. For reliability we developed RAID, network-attached storage and storage-area networks that required the installation of more complex data center storage management processes.

The latest answer to this dilemma is storage virtualization, which adds a new layer of software between storage systems and servers.  Network management no longer needs to know where specific drives are located. The management of partitions or storage subsystems, or the identification of where data resides now becomes a task for the virtualization software. Administrators can identify, provision and manage distributed storage as if it were a single, consolidated resource available across an entire network.

Availability increases with storage virtualization, since applications aren’t restricted to specific storage resources. Data access is thus insulated from failure of a particular disk capacity. This automates the expansion of storage capacity and reduces the need for manual provisioning in supporting a specific applications. Storage resources can be updated on the fly without affecting application performance, thus reducing and even eliminating downtime.

Storage virtualization operates as an intermediate layer. It becomes the primary interface between servers and storage. Servers see the virtualization layer software as a single storage device, while all the individual storage devices see the virtualization layer as their only server. This makes it possible to group storage systems—even devices from different vendors and different data base software solutions—for unified management.

Storage virtualization shields servers and applications from hardware or software changes to the storage environment, letting users easily hot swap a disk. Data copying and data-backups are also managed at the virtualization layer. For instance data replication, whether for snapshot or disaster recovery to different data centers can be handled by the virtualization system, as a background task, with a shared management interface.

Because data can be moved at will, vulnerable data centers or outdated storage capacity can be moved to the best storage devices. The virtualization software or device is responsible for maintaining a consistent view of all the mapping information for the virtualized storage, which defines meta-data and is stored as an overarching mapping table. Storage virtualization can be structured to look up metadata in the virtual disk space for data discovery and for de-duplications.

Technology Maturity
Storage virtualization can be considered a mature technology with F5 Networks and Citrix ranked as the leaders in the ability to execute.  There are other vendors such as 3PAR, Compellent Technologies, DataCore Software, Hitachi Data Systems, IBM, StarWind Software and Violin Memory. Storage virtualization has origins in 1980’s but has become widely adopted with the large-scale virtualization of data center servers.

Implications

Storage virtualization, in addition to offering savings in the utilization of disk capacity, enables improved real-time interoperability of data extracted from dissimilar data sources. DoD can now migrate its data files, which are presently wedged into incompatible servers, to an environment where pooled data services and universally shared metadata become economically feasible.