HP Fabric OS 7.1.0, Administrator'S Manual

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120 Fabric OS Administrator’s Guide
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Routing policies
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Device-based routing
Device-based routing optimizes routing path selection and utilization based on the Source ID (SID)
and Destination ID (DID) of the path source and destination ports. As a result, every distinct flow in
the fabric can take a different path through the fabric. Effectively, device based routing works the
same as exchange-based routing but does not use the OXID field. This helps to ensure that the
exchanges between a pair of devices stay in order.
NOTE
Device-based routing requires the use of the Dynamic Load Sharing (DLS) feature; when this policy
is in effect, you cannot disable the DLS feature.
Device-based routing is also a form of Dynamic Path Selection (DPS). DPS assigns communication
paths between end devices in a fabric to egress ports in ratios proportional to the potential
bandwidth of the ISL, ICL, or trunk group. When there are multiple paths to a destination, the input
traffic is distributed across the different paths in proportion to the bandwidth available on each of
the paths. This improves utilization of the available paths and reduces possible path congestion.
NOTE
Device-based routing is supported in FICON environments only.
AP route policies
Two additional AP policies are supported under exchange-based routing:
•
AP Shared Link policy (default)
•
AP Dedicated Link policy
NOTE
AP policies are independent of routing policies. Every routing policy supports both AP policies.
The AP Dedicated Link policy relieves internal congestion in an environment where:
•
There is a large amount of traffic going through both directions at the same time.
•
There is a reduction of the effect of slow devices on the overall switch performance.
It is recommended that the default AP Shared Link policy be used for most environments. Also, it is
recommended that you design a SAN that localizes host-to-target traffic by reducing the amount of
traffic through the router.
ATTENTION
Setting either AP route policy is a disruptive process.
Routing in Virtual Fabrics
Virtual Fabrics support DPS on all partitions. DPS is limited where multiple paths are available for a
logical fabric frame entering a Virtual Fabrics chassis from a base fabric that is sent out using one
of the dedicated ISLs in a logical switch.
The AP policy affecting the DPS behavior, whether it is exchange-based, device-based, or
port-based, is configured on a per-logical switch basis. In-order delivery (IOD) and DLS settings are
set per logical switch as well. IOD and DLS settings for the base switch affect all traffic going over
the base fabric including any logical fabric traffic that uses the base fabric.