FW V06.XX/HAFM SW V08.02.00 HP StorageWorks SAN High Availability Planning Guide (AA-RS2DD-TE, July 2004)

Physical Planning Considerations
161SAN High Availability Planning Guide
Devices in common zones can be prohibited from communicating through
SANtegrity Binding or PDCM arrays, but hard zoning takes precedence over
preferred path configurations, allowed connectivity through soft zoning, or
device-level access control.
4. 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 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.
5. 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
that a list of devices is in the same zone as the requesting device it 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.
6. 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 Binding, PDCM
arrays, zoning, preferred paths, and device-level access control. It is
recommended to follow the best practices listed here in order of precedence.