Storage Area Networks For Dummies®

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Par t II: Designing and Building a SAN
Your SAN plan will also use fabric zoning and LUN security to ensure that the
two different operating systems are isolated and don’t interfere with each
other’s performance or data integrity. (Our user community is overly cautious
about its data.)
Fabric Zoning 101
Zones, zone sets, aliases . . . what are all these things? A zone is a bunch of
ports or World Wide Name (WWN) addresses that are isolated together into
a group. Only members within the group can see each other and communicate
among themselves. Think of it like a phone conversation: If you want to
talk to Aunt Betsy on the phone, you dial the number (her phone number is
like a World Wide Name), and the phone company puts your phone and Aunt
Betsy’s into a zone. When you’re connected, nobody else can communicate
with your phone or Aunt Betsy’s, but your two phones can communicate
with each other. If you want to bring Aunt Polly into the conversation, you
can have a three-party call by adding Aunt Polly’s number into this zone, and
then the three of you can all chat with each other. (For more on World Wide
Names, review Chapter 3.)
Because the phone company obviously deals with more users than just you and
your two favorite aunts, millions of these zones are in use simultaneously —
making up a zone set. A zone set is a given group of zones that, when activated,
becomes the current configuration that a particular switch or fabric uses to
enforce the rules of who can talk to whom.
You can have only one zone set active. All the others are on standby, waiting
in the wings to be activated if need be.
Members of zones have names such as Domain 4, Port 16, or 6a:0f:5c:ae:81:9c:a8:4f.
Because these names aren’t easy to understand, someone came up with a
way to give them nicknames, or aliases. A zone alias is just a friendly name
used to refer to a real WWN or port address within a SAN fabric.
For example, you can give your HBAs’ WWNs aliases of UNIXBOX-1 and
UNIXBOX-2, give your storage array’s ports aliases of ARRAY1-A, and so on.
Then, when you want the HBAs to see the array’s ports, you create a zone
called UNIXBOX with members UNIXBOX-1, UNIXBOX-2, and ARRAY1-A.
Add this new zone to the active zone set and activate it. Now both HBAs on
your UNIXBOX server can see and communicate with the storage array port
ARRAY1-A through the switch fabric of your SAN.
This type of zoning is soft zoning because you’re using the WWN address in
the zone (even though it’s an alias in this case, that doesn’t make a difference).
The beauty of soft zoning is that no matter what port you plug the cable into
within the fabric, the WWN is the same — therefore, the zone still works. Some
people didn’t like that idea, and they wanted to control which physical port