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Designing a large storage area network (SAN) fabric is a complex job. Overprovisioning a SAN will run up the costs substantially, and an underperforming SAN can be equally costly. SAN design tools from Computer Associates, EMC, Hewlett-Packard and other companies are starting to appear, and these products can take some of the guesswork out of constructing a well-tuned SAN.

"As users move to heterogeneous, fabric-attached storage environments, the complexity of managing the increasingly diverse number of devices and the associated levels of software versions increases the effort required to define a solid design and to test the impact of any change," says Carolyn DiCenzo, research VP of storage management software, at Gartner Inc. "There is clearly a need for software to automate this effort, supporting the design and reducing the risk as changes are made to the environment."

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What to look for in a SAN design tool
Does it work with all manufacturers' components or only a limited set? Some storage area network (SAN) design programs were originally designed to help their sales forces sell their companies' products. The tools couldn't work with other vendors' products. In designing a new SAN or modifying an existing one, the more SAN components the tool works with, the more flexibility it will have in designing the SAN that best meets your company's needs.
Can the tool modify an existing SAN? As SANs grow, this is an important feature. The ability of the tool to audit a SAN and determine what's attached to what and identify the version number of each component is helpful in maintaining the SAN. And when one company is acquired by another, the SAN design tool's ability to discover components and perhaps merge two or more SANs is an invaluable feature.
Is the company that sells the SAN design tool committed to improving it?
Does the SAN design tool work with new SAN protocols such as switched Ethernet and Fibre Channel?
Can the SAN design tool's algorithms respond to specific goals such as designing a SAN with the lowest cost that meets certain performance metrics?

To help design its internal SANs, Hewlett-Packard (HP) developed a set of tools collectively called "Appia, after the Appian Way, one of the networks of roads leading to ancient Rome," says Julie Ward, project scientist at the decision technologies department, HP laboratories, in Palo Alto, CA. HP recently renamed Appia, and it is now called HP SAN Designer.

HP SAN Designer can design Fibre Channel (FC) SANs and in the "near future," Ethernet SANs, an HP spokesperson says. It works with a variety of storage products, not just HP gear. Ward claims that HP SAN Designer can reduce the cost of a SAN by a factor of three over a manual design.

"But even more important than the cost savings is that the designs can be built--they honor the physical constraints of the system and produce the desired degree of reliability. It is very difficult to verify correctness when designing a large-scale SAN manually," Ward says.

Even if a manually designed SAN works, it may not work optimally if the fault-tolerance aspects are not fine tuned. And in many cases, it's difficult to grow a poorly designed SAN to include hundreds--or even thousands--of storage devices.

HP SAN Designer's algorithms and similar SAN design tools balance SAN criteria such as work loads, device performance, protection levels, disaster tolerance and overall performance demands to configure the storage fabric. HP SAN Designer can analyze data flows at a granular level. From each host to each storage device, it suggests the preferred data paths and load balancing. In addition, HP SAN Designer can automatically modify the SAN as it grows and evolves, according to Thomas Goepel, HP's portfolio manager for storage services.

HP SAN Designer isn't sold or licensed. "The use of the tool is part of the standard HP SAN design delivery," says Goepel, adding, that in the future, the tool will be "more tightly integrated into HP's sales tools."

EMC is also jumping on the SAN design tool bandwagon with SAN Architect, a new Web-based software program for SAN design, modeling and validation. The template-driven SAN Architect is particularly suited for customers with rapidly changing SAN environments, planned multiple server, switch or array rollouts and consolidations and even those who simply need to validate changes or implementation plans without interrupting production systems.

SAN Architect guides storage architects and IT administrators through the design and validation of a fully functional SAN. It ensures that proposed changes are accurate and precise by modeling and validating hosts, host bus adapters (HBAs), switches and storage arrays, producing a final design that's 100% supported by EMC.

According to Randy Carter, a SAN architect at Radian Group Inc., in Philadelphia: "Before SAN Architect, SAN design involved consulting numerous compatibility reference sources, manually white boarding out the flows, building a Visio presentation and, finally, creating an Excel spreadsheet to fit everything together. What used to take 24 hours now takes four."

This was first published in July 2003

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