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Technologies for scaling beyond a single fabric

A key technology for enabling storage networks to span single fabrics and locations is a storage network router.

A key technology for enabling storage networks to span single fabrics and locations is a storage network router. Vendor and marketing hype aside, there are generically three types of functions that storage networking routers perform:

  • Segmentation and inter fabric routing (not to be confused with partitioning).
  • Protocol conversion (not to be confused with mode conditioners).
  • Storage over distance enablement using IP, SONET/SDH and optical networks.
Storage over distance support includes FCIP tunneling based products, iFCP, and storage over SONET/SDH generic framing protocol (GFP) products. Some products that support a single function, for example, protocol conversion, are also known as bridges and gateways. Protocol conversion includes Fibre Channel (FCP) to Ethernet (iSCSI), Fibre Channel (FCP) to parallel SCSI, FICON to Fibre Channel (FCP), and ESCON to FICON Bridge. Segmentation products enable independent fabrics to be physically connected, yet remain logically isolated.

The emergence of SAN segmentation and inter-SAN fabric routing capability is enabling SAN sub networks to be created. For example, if you connect two SAN fabrics together, they will be merged into a single fabric. The result will be a combined SAN fabric that could have device and address conflicts and a proliferation of state change and management traffic across both networks. Segmentation also can be used to isolate management traffic from different fabrics and keep traffic local. Some products only support a single function such as protocol conversion or distance enablement. Other products support two or more functions and others from vendors including Brocade (Multi-Protocol Router), Cisco (MDS 9216i) and McData (Eclipse) support all three basic routing functions.

The following table shows technologies that can be used to support different storage functions for scaling on a local and remote basis, for example using iSCSI and FCP for block storage access and NAS for file-based access. Not shown in the table below are vendor-unique technologies that support such functions as segmentation and partitioning.

Storage Network Scaling Technologies
Block Storage Access No Yes No Yes No
File Storage Access No No No No Yes
Storage Sharing No Yes No Yes Yes
Storage over Distance Yes Yes Yes Yes Yes
SAN Fabric Segmentation No No Yes No No
Tunneling Fibre Channel Yes No No No No
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About the author: Greg Schulz is a senior analyst with the independent storage analysis firm, The Evaluator Group Inc. Greg has 25 years of IT experience as a consultant, end user, storage and storage networking vendor, and industry analyst. Greg has worked with Unix, Windows, IBM Mainframe, OpenVMS and other hardware/software environments. In addition to being an analyst, Greg is also the author and illustrator of Resilient Storage Networks, Greg has contributed material to Storage Magazine. Greg holds both a computer science and software engineering degree from the University of St. Thomas.

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