This column concludes the series on storage networking architectures by defining the "in-band ESCOM" model which can be looked at as a combination of four of the previously defined models. By combining components
The telecom architecture forms the outer layer of this model. Servers are connected to this model based upon the strengths they may draw from today's networking models. Quality of Service (QoS), advanced routing protocols, management consoles and advanced networking protocols all come bundled with today's networking architectures. But maybe most important, this model also offers established security methodologies that will become increasingly important in the emerging enterprise storage infrastructure.
The "in-band" appliance creates a new layer between the telecom and ESCON architectures while interconnecting them as well. This appliance serves three major purposes. First, it minimizes one of the telecom's main drawbacks in a storage network, the routing tables. Since all storage traffic may be routed to this device (which can control all storge devices), it simplifies the increasingly complexity found in a large telecom model. Second, it allows all storage to be configured and discovered by the in-band appliance. All storage devices may now be connected to the ESCON model, minimizing or eliminating the current LUN masking and zoning headaches SAN administrators currently face. Finally, it allows organizations to keep their existing infrastructure in place and gradually grow into this environment.
The final piece of this puzzle, the ESCON architecture, serves as the foundational layer to which all storage and tape devices are connected. The ESCON architecture boasts high availability and reliability in conjunction with simplicity of management without introducing the routing, security and management headaches found in the telecom model as this level in the SAN.
This "in-band ESCOM" model presents a powerful new model of connecting disparate storage devices, networking protocols, and operating systems. It offers the appropriate levels of scalability, flexibility, simplicity and security at the different points in the SAN infrastructure. But as important, it allows for the decoupling of various computing disciplines, namely storage administration, network administration and performance monitoring, each highly technical in their own right. With the increasing likelihood that network based virtualization will arise, this model is sure to follow as companies look to use what they have in a manner that both lowers costs and makes the best use of their existing resources.
Read Part I: Design concepts for storage networks
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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
This was first published in July 2003