HP StorageWorks Fabric OS 6.x administrator guide (5697-7344, March 2008)

Fabric OS 6.x administrator guide 207
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