SAN on the move

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 Centre'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 modelling, 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), provides some healthy perspective on managing the new realities -- and risks -- of today's complex SAN deployments. His company, which manages pharmacy benefits and processes drug cards, has grown considerably during the past five years.

The company'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 centre and a disaster-recovery site in a neighbouring 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.

Previously, this meant developing and running custom scripts, Kudaravalli says. Now, using HP Storage Essentials (formerly from AppIQ), he can extract the information with just one press of a button. Also gone is the tedious work of maintaining the Visio diagram that depicted relationships between the SAN's components. Instead, Storage Essentials creates and updates a network map on one screen that shows how the StorageWorks EVA box is connected to the switch and all the hosts, he says.

Keeping tabs on this complex SAN environment and trends in application-specific usage is much different to the days of servers with direct-attached storage, Kudaravalli says. "Most people still see storage as a disk drive attached to a server box. But, it's not when you are talking about hundreds of hosts and terabytes of storage all needing to be aligned and planned in order to prevent performance issues," he adds.

A company needs to be careful even when determining which ports to assign to which application hosts, he says. "You can't connect all your lights to the same power source, or you'll blow a fuse. The same thing applies to managing and redistributing the load of applications correctly among the various Fibre Channel ports in use on your SAN. Storage Essentials helps us identify which ports make sense to use, based on their load."

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