FW 05.01.00 and SW 07.01.00 HP StorageWorks SAN High Availability Planning Guide (AA-RS2DC-TE, June 2003)

Planning Considerations for Fibre Channel Topologies

83SAN High Availability Planning Guide

Special consideration must also be given to applications with high data

transfer rates or devices that participate in frequent or critical data transfer

operations. For example, in Figure 35 on page 78, suppose device D

is a

server and device D

is a storage unit and both devices participate in a critical

nightly backup operation. HP recommends that such a connection be routed

directly through Director S

(rather than the entire fabric) through zoned or

WWN-bound port connections. For additional information, refer to “Device

Locality” on page 100.

■ 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 Zones” on page 133.

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:

■ 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.