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

Table Of Contents

Planning Considerations for Fibre Channel Topologies

69SAN High Availability Planning Guide

Planning for Private Arbitrated Loop Connectivity

Private arbitrated loop topology supports the clustering of isolated servers and

storage subsystems into workgroup or departmental SANs. This topology is

well-suited to small-sized and mid-sized configurations where modest

connectivity levels and high data transmission speeds are required. The topology

also supports low-cost switching and connectivity in environments where the

per-port cost of a director is prohibitive.

Private arbitrated loop topology:

■ Supports the connection of up to 125 node (device) ports.

■ Reduces connection costs by distributing the routing function through each

loop port (loop functionality is a small addition to normal Fibre Channel port

functionality).

■ Provides a fully blocking architecture that allows a single connection between

any pair of loop ports at any time. Connections between a third loop port and

busy ports are blocked until communication between the first connection pair

ends.

Shared Mode Operation

When set to shared mode, a loop switch implements standard Fibre Channel

arbitrated loop topology and distributes the frame routing function through each

loop port. Shared mode operation and its simplified logical equivalent are

illustrated in Figure 27.

Figure 27: Shared Mode operation and logical equivalent

Part A of Figure 27 shows device D

connected to server S

through a pair of

H_Ports and communicating at 1.0625 Gbps. Although the remaining switch

H_Ports (six ports) and device D

are unavailable for connection, frame traffic

H_Ports

Logical Equivalent

Loop Switch