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Mixing Fibre SANs with fiber IP networks

What are the advantages and disadvantages of mixing Fibre SANs with fiber IP networks (with fiber switches)? Any troubles for the SAN administrator?

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Fibre-based IP networks are commonly used when the transport is Gigabit Ethernet. Faster transports benefit from optical networks since they run at the speed of light, are harder to tap, enhance security and can be used as a connection medium over long distances.

The backbone for the Internet is optical.

"Fibre" SANs are different than "fiber" IP networks, other than the reversal of the "re" at the end of the word fiber.

SANs use the Fibre Channel protocol and IP networks use the TCP/IP protocol. Therefore, you need different hardware to connect everything together.

IP network switches come from vendors like Cisco, 3Com, F5, Catalyst, etc.

SAN switches come from vendors like Brocade, McData, Inrange, Qlogic, etc. and now Cisco.

The frame types, data types, routing mechanisms, name services, etc. are all different between SAN and TCP/IP. But they are both nothing more than optical networks. If you understand one, you will have no trouble understanding the other. SAN and IP are getting closer these days with the advent of iSCSI that uses block-based SCSI data that is encapsulated into IP frames.

With iSCSI, your IP folks can now leverage their knowledge of IP networking, because it all applies to iSCSI with a few differences.

There ARE SAN host bus adapters that enable you to use IP over the SAN fabric. There were some issues with certain SAN switch microcode versions and interaction with adapter firmware and driver versions when this stuff first came out. Also, some of the SAN vendors don't like you to mix traffic. Make sure you contact your SAN vendor and make sure you will be supported before attempting IP over SAN. Also, contact your switch vendor and ask them what firmware versions and HBAs are supported for IP. By the way, some adapters also support VI over SAN which is GREAT for fast cluster connections!

Chris

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This was first published in January 2003

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