The Search for Sentient SANs Page 4 -

The Search for Sentient SANs Page 4

Current Virtualization Just the Beginning

Although virtualization in the form of storage pooling is a good beginning, the potential for automating storage processes is much greater. Representing different types and capacities of storage as a single resource avoids the labor-intensive configuration of individual storage devices. With additional intelligence, however, it should also be possible to dynamically assign resources based on the unique requirements of specific applications.

Application-aware virtualization requires monitoring of storage transactions to identify the most appropriate form of storage that should be applied. Streaming video, for example, is best allocated to the outer tracks of disks so that minimal head movement will result in more consistent streaming. Online transaction processing is best stored on high availability RAID with immediate synchronous data replication to provide a readily accessible copy of the most current business orders.

Additionally, policy engines may automatically determine which hierarchical storage management (HSM) routines should be applied to particular data types. In financial enterprises, for example, high-availability storage for stock transactions may need synchronous disk-to-disk replication, secondary disk-to-tape, and, as the data ages, tape-to-optical for long term storage. Less critical applications may only require periodic backup to tape. By examining the data type issued by a host or server, policy intelligence can apply predefined rules on how that data should be treated and which conduits within the SAN should be enabled to expedite policy enforcement.

Although some vendors are currently offering limited versions of application-aware and policy-based HSM, the missing component is tight integration into the SAN infrastructure to minimize data handling and movement. SAN management applications in general and virtualization have trailed behind the evolution of SAN hardware, and the next several years will see increasing intelligence through software and optimized hardware to fully exploit the power of networked storage. This in turn will make storage networking far more productive and ubiquitous as an obvious choice for enterprises large and small.

Tom Clark
Director of Technical Marketing, Nishan Systems
Author: Designing Storage Area Networks Second Edition (2003) (available at, IP SANs (2002) (also available at

» See All Articles by Columnist Tom Clark

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