Switch-level storage virtualization, page 2

Virtualization allows administrators to gather, organize, allocate and manage storage hardware without regard for the applications or servers that use it. When properly implemented, storage virtualization eliminates forgotten or partially -used disks, allowing superior storage utilization. This demands fewer drives, often translating into significant cost savings. Data can easily be transferred and migrated between storage resources. Virtualization also permits storage resources to be altered and updated on the fly without disrupting application performance, generally reducing downtime. Interest is building in virtualization at the switch level, promising better performance and interoperability.

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Implementing switch-based storage virtualization

Administrators must determine which servers and storage should be attached, identify any necessary server software or storage subsystem upgrades, account for network reconfigurations and lay out any zoning or mapping changes. "There's a good bit of planning there," Garrett says.

Once an adequate plan is formulated, switch-based storage virtualization can be physically implemented on the network by adding an intelligent switch along with its supporting software. One example might be the inclusion of a SilkWorm Multiprotocol Router from Brocade Communications Systems Inc. or an MDS 9500 from Cisco Systems Inc. Either product might run EMC Corp. Invista software for virtualization.

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VMware users want more for storage

Although the physical deployment of an intelligent switch might seem straightforward, users can certainly expect some level of disruption to network service. Replacing an existing switch tends to be more disruptive. Installing a new intelligent switch, in addition to existing infrastructure, is often less disruptive since servers and storage can be transferred to the new switch in phases -- spreading out smaller disruptions over a longer period of time. "Most sites would schedule a day or two to get started," Garrett says. "That would include the configuring and also the training in getting used to the [virtualization management] software interface."

Prospective users must pay very close attention to the management software needed for any new intelligent switch. Existing management tools should manage intelligent switch hardware, allowing zones and assets to be managed the same as legacy switches. However, managing services like replication may demand new software from intelligent switch vendors. Still, analysts note that the industry is moving toward a unified management environment. Garrett points to EMC's recent acquisition of Kashya Inc. as one step in this direction.

Backing out of virtualization

Backing out of a virtualization scheme presents a particular challenge for the enterprise, and some companies are reluctant to deploy virtualization for fear of being locked into a specific vendor -- a concern that analysts echo. While the actual hardware removal isn't terribly difficult, removing the virtualization software from the environment is problematic at best. "Whoever controls the metadata and volume mapping controls the lock-in," Schulz says, noting as an example that it's relatively easy to migrate from a Cisco switch running EMC Invista to a Brocade switch running EMC Invista, but to move from EMC Invista software to StoreAge Ltd. software may present significant problems.

It's important to confer with your virtualization vendor and discuss back out options in detail. Analysts suggest testing the virtualization setup in a lab environment first -- using the virtualization platform as you normally would and then performing the uninstall process yourself. Direct experience will help to identify any problem areas, and test vendor support if needed.

Improving manageability

Storage virtualization has been a significant technology for Friends Provident PLC, a financial services company in the U.K. Almost four years ago, Friends Provident maintained only about 3.5 terabytes (TB). Today, that total has burgeoned to 50 TB across three tiers with no end in sight. Such growth might overwhelm conventional storage management, but virtualizing the storage has brought much more organization and flexibility to the data center. "Our utilization has been much higher throughout that period," says Martin Bruce, lead storage consultant at Friends Provident. "We're able to add chunks of storage on an incremental basis, maybe 4 TB or 8 TB at a time and then bolt that into a virtualized environment, and we're free to use that where we want."

Storage virtualization based on QLogic Corp. hardware and StoreAge software has also brought an unprecedented level of heterogeneous support to the data center. Bruce notes that Friends Provident employs storage hardware from EMC, IBM and HDS within the same virtualized environment while using fewer tools. "This enables us to use a single set of tools to produce low capacity snapshots on arrays from different vendors and migrate data between them with zero downtime," Bruce says, noting that 50 TB are managed across two sites with only two IT staffers.

Heterogeneous storage virtualization makes storage more cost-effective. "This has enabled us to grow our [storage] environment at least 100% each year for the past three years cost-effectively," Bruce says, noting that tiered storage is also easier to manage, since storage can be pooled based on performance and then allocated as needed based on utilization.

Bruce strongly recommends advance testing for performance, stability and compatibility before deployment. "We're fortunate in that we have a test environment on a different site that we can use to test this technology before deploying it into our production data center," he says. "We'll then move to roll it out further across the field because of the added benefits."

Expect a cycle of maturity

Although no one is expecting dramatic changes in switch-based storage virtualization technology, analysts look forward to a period of technological maturity that will affect both hardware and software. "I really don't see anything major from a functionality standpoint," Garrett says. "At this point, we're in a technology maturity cycle -- not an innovation cycle."

Storage services blade hardware should continue its relentless advance forward to provide substantially more processing power, performance and efficiency. Intelligent switch options should appear on products ranging from departmental switches up to the enterprise-class director. As the hardware evolves and becomes more readily available, users should expect corresponding software to leverage those hardware improvements to create more robust and versatile virtualization platforms.

Ultimately, the improving performance and expanding features of switch-based storage virtualization are expected to have a profound impact on adoption. "It's shifting from a focus of 'nice to have' to 'need to have,' " Schulz says, citing a parallel between virtualization and RAID technology. RAID appeared in the '80s but did not emerge as a staple of enterprise storage until the mid-90s.

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This was last published in June 2006

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