Because of the large-scale growth in data, many of today's storage-area networks have evolved considerably from their early, well-contained deployments. Corporate IT executives are pushing SANs to their limits - in size, complexity and functionality - as they embrace New Data Center mandates about tiered storage, storage on demand and delivering storage as a service to key internal customers.

The amount of data in today's enterprise SAN can be measured in multiple terabytes, and may comprise thousands of complex network interconnections. Forward-looking IT organizations have looked for new and creative ways of managing the scale and complexity that go hand in hand with sprawling, networked storage environments. Increasingly, they are employing SAN change-management tools - often a subset of a larger storage resource management arsenal - to meet the New Data Center's stringent performance demands.

To varying degrees, IT executives are using today's crop of SAN change-management tools to navigate and keep tabs on the labyrinth of dual redundant paths that exist on a SAN from host to storage array. The tools typically let administrators follow the trail of these interdependencies, which goes everywhere, from hosts and host bus adapters (HBA) to Fibre Channel switches, ports and storage arrays - even down to the level of logical unit numbers (LUN) and virtual volumes carved out of individual disk drives.

Many SAN change-management tools offer detailed device discovery and topology mapping for homogeneous and multivendor SANs. Some tools also offer real-time system monitoring, troubleshooting and change-violation alerts, functions that directly link to a SAN change-history database they maintain.

Some tools make an effort to follow IT Infrastructure Library (ITIL) best practices for maintaining and updating changes, says John Webster, analyst and partner with the Data Mobility Group. Storage vendors with a strong ITIL focus include IBM and Hitachi Data Systems, he says.

Other tools go a step further and provide predictive change-management functionality. With these tools, storage managers can perform sophisticated what-if analyses and modeling, from which they learn the impact of potential SAN changes before rolling them into production.

Using tools with change-tracking and -monitoring abilities has begun to prove critical for a variety of high-growth SAN environments, including organizations moving to embrace service-centric delivery.

Babu Kudaravalli, director of enterprise systems at National Medical Health Card Systems (NMHC) in Port Washington, N.Y., provides some healthy perspective on managing the new realities - and risks - of today's complex SAN deployments. His midsize company, which manages pharmacy benefits and processes drug cards, has grown considerably during the past five years.

NMHC's storage network has grown five-fold since Kudaravalli joined the company four years ago. Now it houses about 65T to 70TB of data and consists of an HP StorageWorks XP1024 disk array, an XP128 array at a remote site, a few StorageWorks EVA2000 systems and nearly 400 Fibre Channel ports on Cisco MDS switches. It includes NMHC's primary data center in Port Washington and its disaster-recovery site in a neighboring city.

NMHC acquired the StorageWorks arrays under a pay-per-use model, Kudaravalli says. Given this, he says he was particularly interested in tracking system capacity. He wanted to know how much storage each application server used, and how much free capacity was available across the SAN.