HP 316095-B21 - StorageWorks Edge Switch 2/24 Planning Manual page 85

After directors and edge switches are defined and cabled, they automatically join
to form a single fabric through a user-transparent process. However, the user
should be aware of the following fabric concepts, configuration characteristics,
and operational characteristics:
Note:
SAN High Availability Planning Guide
Zoning — For multi-switch fabrics, zoning is configured on a fabric-wide
basis. Changes to the zoning configuration apply to all directors and switches
in the fabric. To ensure the zoning configuration is maintained, certain rules
are enforced when two or more elements are connected through ISLs to form
a fabric, or when two or more fabrics are joined. For additional information,
refer to "Configuring
Principal Switch selection — Setting this value determines the principal
switch for the multi-switch fabric. Select either Principal (highest priority),
Default, or Never Principal (lowest priority) from the Switch Priority
drop-down list. If all fabric elements are set to Principal or Default, the
director or switch with the highest priority and the lowest WWN becomes the
principal switch.
Following are examples of principal switch selection when fabric elements
have these settings.
— If you have three fabric elements and set all to Default, the director or
switch with the lowest WWN becomes the principal switch.
— If you have three fabric elements and set two to Principal and one to
Default, the element with the Principal setting that has the lowest WWN
becomes the principal switch.
— If you have three fabric elements and set two to Default and one to Never
Principal, the element with the Default setting and the lowest WWN
becomes the principal switch.
Note that at least one director or switch in a multi-switch fabric needs to be set
as Principal or Default. If all the fabric elements are set to Never Principal,
all ISLs will segment. If all but one element is set to Never Principal and the
element that was Principal goes offline, then all of the other ISLs will
segment.
HP recommends configuring the switch priority as Default.
In the audit log, note that the Principal setting maps to a number code of 1,
Default maps to a number code of 254, and Never Principal maps to a number
code of 255. Number codes 2 through 253 are not used.
Planning Considerations for Fibre Channel Topologies
Zones" on page 156.
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