Fabric Manager Users Guide, Version 6.1, Revision A - QLogic

4–Virtual Fabrics
Configuration
Quality of Service
Quality of Service allows the priority of each vFabric to be configured. QoS
policies allow multiple applications to run on the same fabric without interference,
through controlling the use of network resources. These policies allow the
following:
• Setting minimum bandwidth percentages for high-volume traffic.
• Addressing needs of high-priority, low-volume traffic.
QoS policies allow the user to assign a bandwidth minimum to classes of traffic to
define how network resources are allocated. For instance, networking traffic can
be assigned to one vFabric, storage to a second vFabric, and compute to a third.
These classes of traffic can then be assigned a bandwidth percentage to which
they will be limited when a link is saturated. Low-volume traffic requires low
latency, like administrative or control traffic, the user can specify this as high
priority.
QoS Operation
Virtual Lanes (VLs) permit multiple logical flows over a single physical link. Each
physical link has a number of VLs. Each class of service has a Service Level (SL).
The local route header of the packets carries the SL, which identifies the different
flows within the subnets. The amount of resources allocated to the VL is based on
the bandwidth configured for the vFabric containing the SL. The Subnet Manager
programs the SL-to-VL mappings and VL Arbitration tables to achieve the QoS
policies.
Applications can query for path records by Service ID to obtain path records
associated with the given application. These path records contain the SL
associated with the traffic class/QoS vFabric. In turn, this SL is used for packets
within this class of traffic.
Configuration
The configuration of vFabrics consists of the following sections:
• Applications — describes applications that can run on one or more end
nodes
• DeviceGroups — describes a set of end nodes in the fabric
• VirtualFabrics — defines a vFabric consisting of a group of applications, a
set of devices, and the operating parameters for the vFabric
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