HP StorageWorks 8/80 HP StorageWorks Fabric OS 6.1.x administrator guide (5697 - Page 233

10 Routing traffic This chapter provides information on routing policies. Data routing and routing policies Data moves through a fabric from switch to switch and from storage to server along one or more paths that make up a route. Routing policies determine the path for each frame of data. IMPORTANT: For most configurations, the default routing policy is optimal, and provides the best performance. You should change the routing policy only if there is a performance issue that is of concern, or if a particular fabric configuration requires it. The following routing policies are available to tune routing performance: • Exchange-based routing The choice of routing path is based on the Source ID (SID), Destination ID (DID), and Fibre Channel originator exchange ID (OXID), optimizing path utilization for the best performance. Thus, every exchange can take a different path through the fabric. Exchange-based routing requires the use of the Dynamic Load Sharing (DLS) feature; when this policy is in effect, you cannot disable the DLS feature. Two additional AP policies are supported under exchange-based routing: • AP shared link policy (default) • AP dedicated link policy The AP dedicated link policy dedicates some links to egress traffic and some to ingress traffic. • Port-based routing The choice of routing path is based only on the incoming port and the destination domain. To optimize port-based routing, DLS can be enabled to balance the load across the available output ports within a domain. Using port-based routing, you can assign a static route, in which the path chosen for traffic does not change when a topology change occurs unless the path becomes unavailable. If the static route violates FSPF, it is not used. In contrast, exchange-based routing policies always employ dynamic path selection. NOTE: For FC routers only: When an FC router is in port-based routing mode, L3 traffic is load-balanced based on SID and DID. When an FC router is in exchange-based routing mode, L3 traffic is load-balanced based on SID, DID, and OXID. Fabric OS 6.1.x administrator guide 233