McDATA StorageWorks 2/140 - Director Switch Planning Manual page 107

When balancing a load across multiple ISLs, a director or switch
attempts to avoid assigning multiple ports attached to a device to
the same ISL. This minimizes the probability that failure of a
single ISL will affect all paths to the device. However, because
port assignments are made incrementally as devices log into the
fabric and ISLs become available, optimal results are not
guaranteed.
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
suppose device D is a server and device D
7
both devices participate in a critical nightly backup operation. It
is recommended that such a connection be routed directly
through director S
2
port connections, WWN-bound port connections, or a preferred
path. For additional information, refer to
• Zoning - For multiswitch 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
After directors and fabric 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 multiswitch 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
fabric switch with the highest priority and the lowest WWN
becomes the principal switch. Following are some 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.
Planning Considerations for Fibre Channel Topologies
Planning Considerations for Fibre Channel Topologies
(rather than the entire fabric) through zoned
Device
Zones.
Figure 3-11,
is a storage unit and
9
Locality.
3
3-23