10Routing Traffic; About Data Routing And Routing Policies; Specifying The Routing Policy - HP AA979A - StorageWorks SAN Switch 2/8V Administrator's Manual

10
Routing traffic

About data routing and routing policies

Data moves through a fabric from switch to switch and 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. Refer to
service" on page 227 for details about VE_Ports.
CAUTION: 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
•
The choice of routing path is based on the SID, 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, the Dynamic Load Sharing feature (DLS) can be enabled to balance the load across
the available output ports within a domain.
Using port-based routing, you can assign a
changes. In contrast, exchange-based routing policies always employ
Port-based routing is supported by all models.

Specifying the routing policy

The following routing policies are supported:
• Port-based path selection
Default on SAN Switch 2/8V, SAN Switch 2/16V, SAN Switch 2/32, SAN Director 2/128, and
4/256 SAN Director (using configuration option 1). These switches support the port-based policy only;
you cannot change the routing policy for these switches. 4/16 SAN Switch and 4/8 SAN Switch, SAN
Switch 4/32, 4/64 SAN Switch, 400 MP Router, and 4/256 SAN Director (using configuration option
5) switches can also use port-based routing.
• Exchange-based path selection
Default on 4/16 SAN Switch and 4/8 SAN Switch, SAN Switch 4/32, 4/64 SAN Switch, 400 MP
Router, and 4/256 SAN Director (using configuration option 5).
Refer to "Configuring
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 option 1, an error message is returned because you cannot change the routing policy.
Refer to the Fabric OS Command Reference Manual for more details on the aptPolicy command.
You must disable the switch before changing the routing policy, and re-enable it afterward.
routing
Directors" on page 109 for more details about 4/256 SAN Director
static route
, in which the path chosen for traffic never
Fabric OS 5.2.x administrator guide 191
"Using the FC-FC routing
dynamic path selection
.