McDATA StorageWorks 2/140 - Director Switch Planning Manual page 236

Physical Planning Considerations
5
McDATA Products in a SAN Environment - Planning Manual
5-32
5. Preferred path - A preferred path provides soft control of fabric
routing decisions on a switch-by-switch or port-by-port basis. The
path instructs a fabric to use a preferred exit port out of a director
or fabric switch for a specified receive port and target domain.
If a preferred path is prohibited by SANtegrity Binding, PDCM
arrays, or hard zoning, the path is not programmed. In addition,
if a preferred path is not a shortest path as calculated by Dijkstra's
fibre shortest path first (FSPF) algorithm, the preferred path is not
programmed. However, preferred paths do take precedence over
dynamic load balancing enabled through the OpenTrunking
feature, soft zoning, or device-level access control.
In general, preferred paths should be configured to influence
predictable or well-known Fibre Channel traffic patterns for load
balancing or distance extension applications.
6. Software-enforced zoning - When a device queries the name
server of a fabric element for a list of other attached devices, soft
zoning ensures only a list of devices in the same zone as the
requesting device is returned. Soft zoning only informs a device
about authorized zoning configurations; it does not explicitly
prohibit an unauthorized connection. Connectivity configured
through SANtegrity Binding, PDCM arrays, hardware-enforced
zoning, and preferred paths takes precedence over soft zoning.
7. Device-level access control - Persistent binding and storage
access control can be implemented at the device level as an
addition or enhancement to other security features (SANtegrity
Binding, PDCM arrays, zoning, and preferred paths) that are
more explicitly enforced.
Security methods described in this section work in parallel with each
other and are allowed to be simultaneously enabled and activated.
Users are responsible for security configuration and operation within
the constraints and interactions imposed by their fabric design and
the methods described here.
Because incompatible security configurations can cause unintended
connectivity problems or shut down Fibre Channel traffic in a fabric,
it is imperative that users study and understand the interactions
between SANtegrity Authentication and Binding, PDCM arrays,
zoning, preferred paths, and device-level access control.