HP AE370A HP StorageWorks Fabric OS 6.x administrator guide (5697-7344, March - Page 203
Routing traffic, About data routing and routing policies, Specifying the routing policy
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9 Routing traffic This chapter provides information on routing policies. About 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 correct path for each frame of data. Whatever routing policy a switch is using applies to the VE_Ports as well. See "Using the FC-FC routing service" on page 215 for details about VE_Ports. TIP: For most configurations, the default routing policy is optimal, and provides the best performance. You should only change the policy if there is a performance issue that is of concern, or 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 these policies are in effect, you cannot disable the DLS feature. • 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 never changes. In contrast, exchange-based routing policies always employ "dynamic path selection." Port-based routing is supported by all HP models. Specifying the routing policy The following routing policies are supported: • Port-based path selection This is the default on 4/256 SAN Director (using configuration option 1). When using configuration option 1, these directors support the port-based policy only; you cannot change the routing policy for these directors. HP StorageWorks 4/8 SAN Switch, 4/16 SAN Switch, Brocade 4Gb SAN Switch for HP p-Class BladeSystem, Brocade 4Gb SAN Switch for HP c-Class BladeSystem, SAN Switch 4/32, 4/64 SAN Switch, SAN Switch 4/32B, 400 Multi-protocol Router and 4/256 SAN Director (using configuration option 5) switches can also use port-based routing. • Exchange-based path selection This is the default on HP StorageWorks 4/8 SAN Switch, 4/16 SAN Switch, Brocade 4Gb SAN Switch for HP p-Class BladeSystem, Brocade 4Gb SAN Switch for HP c-Class BladeSystem, SAN Switch 4/32, 4/64 SAN Switch, SAN Switch 4/32B, 400 Multi-protocol Router and 4/256 SAN Director (using configuration option 5), and DC SAN Backbone Director (short name, DC Director). See "Configuring Directors" on page 25 for more details about 4/256 SAN Director configuration options. You can use the aptPolicy command to display and specify a different routing policy. The aptPolicy command detects the switch's configuration options and provides the appropriate policies for users to select from. For example, if you attempt to set the policy for the 4/256 SAN Director using configuration Fabric OS 6.x administrator guide 207