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

Planning Considerations for Fibre Channel Topologies
119SAN High Availability Planning Guide
— FICON port addressing provides the ability to swap ports for
maintenance. In general, swapping ports in intermix environments does
not affect the practices described. However, if a user implements zoning
using a domain ID and port numbers, zoning information must be updated
contiguous with the port swap operation.
Multiple Data Transmission Speeds in a Single Fabric
The Director 2/64, Edge Switch 2/16, and Edge Switch 2/32 support auto-sensing
of 1.0625 and 2.125 Gbps device connections. The introduction of a higher data
transmission speed to the SAN design provides several benefits and alternatives:
■ High-speed device connectivity — As Fibre Channel devices and HBAs
evolve and become 2.125 Gbps-capable, higher-speed switches are required
to provide basic fabric connectivity.
■ Better fabric performance — As a connection between edge switches, a
2.125 Gbps ISL delivers double the bandwidth of a 1.0625 ISL. Fibre Channel
devices that are not 2.125 Gbps-capable benefit from a higher-speed ISL,
because 1.0625 Gbps traffic is multiplexed and transmitted through the 2.125
Gbps ISL.
■ Additional port count — If additional ISL bandwidth is not required for
fabric performance, 2.125 Gbps connectivity allows the number of ISL
connections to be reduced, thus yielding additional director or switch ports for
device connectivity.
When installing 2.125 Gbps-capable fabric elements in a core-to-edge topology,
deploy the directors or switches at the fabric core to provide end-to-end
high-speed ISL capability. If 2.125 Gbps device connectivity is required, attach
the devices to the core director or switch as Tier 1 devices. If possible, employ
device locality by connecting 2.125 Gbps devices to the same director or switch.
Fibre Channel Distance Extension
Connectivity requirements for a SAN differ from the requirements for a data
network such as a LAN, MAN, or WAN. These differences are summarized as
follows:
■ Data networks (LANs, MANs, and WANs) usually offer best-effort
communication service, relying on upper-level protocols for end-to-end
transport. SANs require high-reliability communications and are intolerant of
data loss or retransmission.