HP StorageWorks Fabric OS 6.1.1 administrator guide (5697-0235, December 2009)

Fabric OS 6.1.1 administrator guide 237
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.
Whatever routing policy a switch is using applies to the VE_Ports as well. See ”Configuring and monitoring
FCIP extension services” on page 385 for details about VE_Ports.
To display the current routing policy and specify a different routing policy, use the aptPolicy command.
The aptPolicy command detects the switch’s configuration options and provides the appropriate policies
for you to select from.
You must disable the switch before changing the routing policy, and re-enable it afterward.
To display the current and supported policies:
1. Connect to the switch and log in as admin.
2. Issue the aptPolicy command with no parameters:
aptPolicy
The current policy is displayed, followed by the supported policies for the switch: