G A L A X Y ® A U R O U R A C O N F I G U R A T I O N A N D S Y S T E M I N T E G R A T I O N G U I D E
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Section 5 Application / Technical Notes
5.3
Fibre Channel Switch Zoning
With Fibre Channel, complexities are shifted from the client to the switch (if
you are using a switch). On the client, no more software is required other than
the driver for the Fibre Channel HBA, and the operating system itself. Instead,
it will focus more on switch zoning concepts.
While it might seem that you can just take a Fibre channel switch out of the
box, just plug it in, and use it, this is not always the case. By default, a Fibre
channel switch usually will act as a hub, but a very powerful one. Any data
coming in from any of the ports (by default) will be sent to all of the other ports
simultaneously. But this is not a good thing: Arrays will try to send data to
arrays, clients will try to send data to clients, and arrays and clients which were
not intended to communicate with each other will communicate. From an array
management standpoint, while this might not be a problem, it creates a lot of
unnecessary traffic on the switch and everything connected to it, which can
have an adverse effect on data rates.
Earlier switches, such as 1GBit switches and some 2GBit switches used a
technique called “provisioning” to govern the connections, however it wasn’t
very efficient from a management point of view (or lack thereof). It worked like
this: The clients are called initiators, and arrays are called targets. You would
flash the firmware on the switch, such that a certain number of ports are
allocated for initiators, and a certain number are allocated for targets. This
would prevent the problems with clients communicating with clients, and
arrays communicating with arrays, but it still didn’t fix the problem with clients
communicating with unintended arrays and vice-versa.
Newer switches are called “fabric switches,” and use what is called “zoning”
instead of provisioning. The term fabric is referring to a meshed grid which is
formed by initiators and targets, with the initiators and targets on the “fringe” of
the grid. This is more advanced, and solves all problems, however there is a
lot of thinking which is involved, and the software can be quite involved. The
key to zoning is being able to mentally visualize the setup.
At it’s simplest, a zone is a fabric “bag” which contains ports. You can usually
zone the switches in such a way, that you can have any number of zones, with
any number of ports in each one, and they can overlap. The zone does not
differentiate between an initiator or target – they are just connection points. So,
using the bag as an example, and a mechanical nut for a target, and bolt for
an initiator. You can have a bag of nuts, a bag of bolts, or a bag of nuts and
bolts.
In more complex setups, you want to avoid the pitfall of creating “mini-
provisioning” problems – to make this easy, you don’t want to have more than
