No SAN is an Island

Like the causeways that link a tapestry of islands and sand bars around the Florida coast, SAN islands are being connected like never before, signaling the emergence of Virtual Storage Area Networks (VSAN).

“A VSAN enables users to tie their existing SAN fabrics into a central ‘core switch,’ protecting the integrity of each fabric,” said Fred Moore, president of Horison Inc. of Boulder, Colo. “VSANs enable different fabrics to exist on the same switch and each is unaware of the existence of other fabrics.”

The problem with stand-alone SAN islands is they can be difficult to manage. If there is a problem, the whole SAN has to come down. SAN routing and VSAN technology makes it possible to isolate parts of SAN. Not only does this make maintenance easier, it also increases your options within the SAN. You can have a virtualized disk library SAN for backup running at 4 Gbps, while the rest of the SAN functions at 2 Gbps. You can also introduce policies on who can manage which parts of the VSAN; for example, certain storage administrators can access one part but not another.

VSAN Options Emerge

There are a variety of different approaches to connecting SAN islands, a technique known in some circles as SAN routing. The Brocade Multiprotocol Router, for example, enables resources on separate fabrics to be shared without merging the fabrics. By adding greater intelligence to the switch, it maintains the practical isolation of SANs, with benefits from a management and operational viewpoint while allowing data to flow between server and storage resources.

“The ability to connect isolated SAN islands is a big step in the evolution of storage networking,” said Tom Buiocchi, vice president of marketing at Brocade. “This is beginning to change how storage networks are designed.”

Brocade’s SAN router supports streamlined data migration, backup and recovery applications. It non-disruptively connects storage and server devices across storage networks by creating Logical SANs (another name for a VSAN) that maintain separate fabric infrastructures. It also enables hierarchical routed connectivity, easier fault isolation and simplified administration. Data center managers can also share high-value storage resources, such as shared backup or replication resources, across multiple servers in multiple fabrics with minimal changes to the existing network design.

HP, too, has added what it calls virtualized multi-protocol routing capabilities to its switch infrastructure. The FC, iSCSI and FCIP protocols are supported as a means of lowering the cost of SAN extension and making SANs easier to manage. The HP StorageWorks Multi-protocol Router uses subnet routing technology to isolate SAN islands. Thus customers can share devices like arrays and tape libraries between SANs without increasing stability risks.

Cisco Systems has also introduced the Cisco MDS Multi Layer Data Center SAN Switch. It functions with multiple protocols (FC, FCIP, iSCSI and FICON), all supported with the same management. Its VSAN technology permits logical partitioning of SANs so you can consolidate individual SAN fabrics into one. Inter VSAN routing allows communication between the SANs without meshing the fabric together. Result: you can back up multiple VSANs to a common pool of backup devices instead of backing up each SAN fabric separately.

Without Inter VSAN routing, for example, you could have 15 percent utilization on one tape system and the other running at 75 percent. But with the establishment of a VSAN, you take one switch, partition it into logical segments, and optimize utilization rates throughout the SAN. This arrangement heightens security since no communication or traffic can flow between the partitions, and it also adds central management.

Which VSAN?

Products are now on the market from Cisco, HP and Brocade, and McData is coming out with a VSAN product too. So which one should you choose? Being a user of the various tools rather than their manufacturer, EMC is in a good position to offer advice. The company’s director of storage networking, Marty Lans, offers some tips to see which might be right for a specific environment.

To his mind, the strength of Cisco is having a unified network. If you have a Cisco-based LAN, it might make sense to bring the SAN into that network for ease of management. McData, on the other hand, has a reputation in the largest SAN environments. So if you have a large site, McData is certainly one to consider. But if you have a more distributed or switch-based SAN, then Brocade may be more appropriate.

“Whichever technology is used, SAN routing and multi-protocol support are big news in the SAN world,” said Lans. “We plan to leverage them to extend the SAN and make management much easier.”

Article courtesy of Enterprise IT Planet

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