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Design concepts for storage networks: Out-of-band telecom

Bits & Bytes: Does out-of-band telecom make sense for you? On the surface this seems like a good model for those trying to boost utilization -- but there are some hidden pitfalls.

Design concepts for storage networks: Part 4

This column defines the third of five storage networking architectures, the "out-of-band telecom" model, which represents one found in a segment of storage networking environments today. This model possesses three distinct characteristics. First, it manages and reports on where data lies on the storage devices. Second, it lies outside of the data path of the storage network itself. Third, the switch itself contains more intelligence.

Discussed in an earlier column in this series, the "out-of-band" technology permits storage administrators to report on and manage the path of the data through the storage network outside of the data path. Through the use of server agents, administrators may discover how much storage each server has and optionally may provision additional storage for those servers that need it. The agents accomplish this task by communicating with a central management server from which the actual administration is done.

The term "telecom" comes from the networking models in existence today that handle functions like Internet and phone switching. Switches that fit into this model support advanced features such as Quality of Service (QoS), trunking between switches (which enables multiple physical paths between switches to function as one logical path), and security capabilities that authenticate the log-in of devices into the fabric.

On the surface, this model makes sense for organizations that have small or large SANs they wish to link together to maximize storage utilization. However, a couple of caveats exist with this approach. First, designing a fabric that interconnects these switches requires far more skill and forethought than deploying only one or two switches. Second, the software running on these switches are much more complex so more advanced skills are needed after the initial deployment to manage and grow the fabric.

This "out-of-band telecom" model merits consideration where it can be appropriately designed and then staffed after deployment. While the telecom model itself offers a scalable and flexible model, the out-of-band storage management component of it in large deployments makes managing the storage so complex that it drains much of the desirability of this solution away.

Yet vendors involved with the development of intelligent switches are well aware of the storage management complexities of this model and, in the next column, we will look at another model that helps to solve the storage management complexities of the "out-of-band telecom" model.

Read Part I: Design concepts for storage networks

About the author

Jerome Wendt is a independent writer and storage analyst specializing in Open Systems storage and storage area network technologies. He currently manages storage and explores new storage technologies for a large organization in this capacity. Jerome may be reached at

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