Today, the Baylor system manages 200TB of data, including patient records and university operations data. HDS hadn't yet released its TagmaStore array, so Layton deployed NetApp V-Series appliances instead. Baylor's use of storage virtualization is mainly to pool storage resources, although the college is also considering how to use the technology to implement data lifecycle management, where patient data can be highly available during treatment but later moved to lesser systems for analysis, auditing, or other needs.

Dallas-Fort Worth International Airport had a different problem. It stored flight data (such as passenger lists, arrival times, baggage tracking, and gate information) in two SANs using Oracle RAC (Real Application Clusters). Oracle RAC could treat one storage target as the primary target and then replicate to secondary systems, but this process simply took too long, recalls John Parrish, associate vice president of terminal technology. If one terminal's SAN goes down, the other SAN has to step in immediately so flight boarding and baggage handling isn't delayed. DataCore's SANsymphony appliance made Oracle RAC think it was working with just one SAN, and Parrish has seen no latency issues crop up in this deployment.

Replication issues were also a problem for Freeze.com. The online retailer needed to keep its 400GB Microsoft SQL Server transaction databases in sync with its reporting databases, but SQL's resource requirements prevented the reporting tools from working on the same database as the transaction management, recalls Freeze.com IT director Kyle Ohme. He would mirror the database periodically, but replication took so long that the reporting database was hours behind, preventing the kind of analysis needed to manage supplies properly. Ohme deployed tools from FalconStor to pool the storage into a virtual volume so both sets of applications can access it in real time. That way, he could send snapshots of the transaction database to the reporting tools, rather than replicate the entire thing.

A Long-Term Effort

Although the storage virtualization promises touted in 2000 turned out to be premature, today's technology does deliver at least the first step toward an automated, self-managing storage infrastructure that functions more as an IT utility, notes Gartner's Zaffos. But that version of storage virtualization is many years away.

One reason is economics. The storage vendors can't afford suddenly to lose the profits from their hardware businesses if storage hardware becomes a commodity managed by software tools. As a result, they're only likely to take measured steps to support the independent standards needed by third-party management tools, Zaffos says.

Operating system vendors may help force the issue if they adopt some of the Storage Networking Industry Association standards, such as Volume Shadow Copy Service, and start moving storage virtualization from network/storage middleware to the OS, says George Teixeira, CEO of DataCore. In fact, IDC's Villars says that in five years Microsoft Windows could implement storage virtualization for mid-tier enterprise deployments.

Another impediment to the grander storage-virtualization vision is that the large enterprises that benefit most from storage virtualization are the most conservative in deploying new technology, since their risk of failure is greater. "We're not seeing the deployments pushing to the technical extreme," Villars says.

The third reason is that the tools are still immature. Current tools focus on giving IT a common console for managing storage. Over time, vendors will begin to add automation and policy-based intelligence for provisioning storage and managing data migration and replication. But because of the complexity of the infrastructure that such tools must manage, "I don't see it for years and years," says Tom Clark, director of solutions and technologies at McData and author of --Storage Virtualization(Addison-Wesley, 2005). In the interim, IT should expect to see point solutions such as heterogeneous replication and snapshots, he says.

But none of these factors prevent enterprises from benefiting from storage virtualization today. In the immediate term, companies should apply virtualization to solve specific problems, such as easing data migration or pooling data across SANs. As time goes on, IT can incrementally broaden its use of the technology, taking advantage of the continued improvements vendors will make over the coming years.