HP StorageWorks 2.128 SAN Director Switch - Manual (Page 97)

Fabric OS 5.x administrator guide 97
6 Routing traffic
This chapter describes HP StorageWorks switch routing features and procedures.
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.
CAUTION: For most configurations, the default routing policy is optimal, and provides the best
performance. Change the policy only 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
• Device-based routing: The choice of routing path is based on the Fibre Channel addresses of the SID
and the DID, improving path utilization for better performance. Thus, the same route is always used
and the sequence of exchanges is guaranteed.
• 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.
Device-based and exchange-based routing require the use of DLS; when these policies are in effect, you
cannot disable the DLS feature.
Using port-based routing, you can assign a static route, in which the path chosen for traffic never
changes. In contrast, device-based and exchange-based routing policies always employ dynamic path
selection. Port-based routing is supported by all HP StorageWorks models (except the 4/256 SAN
Director using configuration option 5; see Table 17 on page 91).
Specifying the routing policy
The following routing policies are supported:
• Port-based path selection: The default on SAN Switch 2/8V, SAN Switch 2/16V, and SAN Switch
2/32, Core Switch 2/64, SAN Director 2/128, and 4/256 SAN Director (using configuration
options 1 through 4). These switches support the port-based policy only; you cannot change the
routing policy for these switches. The 4/8 SAN Switch, 4/16 SAN Switch, 4Gb SAN Switch for HP
p-Class BladeSystem, and SAN Switch 4/32 can also use port-based routing.
• Device-based path selection: Available on 4/8 SAN Switch, 4/16 SAN Switch, Brocade 4Gb SAN
Switch for HP p-Class BladeSystem, and SAN Switch 4/32, and 4/256 SAN Director (using
configuration option 5). If there are devices in your fabric that cannot accommodate out-of-order
exchanges, use the device-based policy. In FICON environments device-based routing is
recommended.
• Exchange-based path selection: The default on the 4/8 SAN Switch, 4/16 SAN Switch, Brocade 4Gb
SAN Switch for HP p-Class BladeSystem, and SAN Switch 4/32, and 4/256 SAN Director (using
configuration option 5).
See ” Configuring Core Switch 2/64, SAN Director 2/128, and 4/256 SAN Director ” on page 87 for
details about 4/256 SAN Director configuration options.
You can use the
aptPolicy
command to display and specify a different routing policy. Note that if you
attempt to set the policy when the 4/256 SAN Director uses configuration options 1–4, an error message
is returned. See the HP StorageWorks Fabric OS 5.x command reference guide for details on the
aptPolicy
command.