About The Dwrr Traffic Scheduler Queue; Changing The Weight In A Dwrr Queue; Displaying Data Traffic Information - HP Cisco MDS 9020 - Fabric Switch Configuration Manual

QoS
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m

About the DWRR Traffic Scheduler Queue

The Cisco SAN-OS software supports four scheduling queues:
•
•
The DWRR scheduler services the queues in the ratio of the configured weights. Higher weights translate
to proportionally higher bandwidth and lower latency. The default weights are 50 for the high queue, 30
for the medium queue, and 20 for the low queue. Decreasing order of queue weights is mandated to
ensure the higher priority queues have a higher service level, though the ratio of the configured weights
can vary (for example, one can configure 70:30:5 or 60:50:10 but not 50:70:10).
Table 56-2
Table 56-2
Source Module Type
Generation 1
Generation 1
Generation 2
Generation 2

Changing the Weight in a DWRR Queue

To associate a weight with a DWRR queue, follow these steps:
Command
Step 1
switch(config)# qos dwrr-q high weight 10
switch(config)# no qos dwrr-q low weight 51

Displaying Data Traffic Information

The show qos commands display the current QoS settings for data traffic (see Examples
Example 56-3 Displays the Contents of all Class Maps
switch# show qos class-map
qos class-map MyClass match-any
Cisco MDS 9000 Family CLI Configuration Guide
56-10
Strict priority queues are queues that are serviced in preference to other queues—it is always
serviced if there is a frame queued in it regardless of the state of the other queues.
QoS assigns all other traffic to the DWRR scheduling high, medium, and low priority traffic queues.
describes the QoS behavior for Generation 1 and Generation 2 switching modules.
QoS Behavior for Generation 1 and Generation 2 Switching Modules
Destination Module Type QoS Behavior Description
Generation 1
Generation 2
Generation 1
Generation 2
match destination-wwn 20:01:00:05:30:00:28:df
match source-wwn 23:15:00:05:30:00:2a:1f
Chapter 56 Configuring Fabric Congestion Control and QoS
QoS behavior reflects the DWRR configuration
for traffic coming in through a given port and
queued to the same egress port. All the other
traffic share equal bandwidth.
QoS behavior reflects the DWRR configuration
for traffic coming in through a given port and
queued to the same egress port. All the other
streams share equal bandwidth.
Bandwidth partitioning is equal for all the traffic.
QoS behavior reflects the DWRR weights
configuration for all possible streams.
Purpose
Associates a relative weight (10) to a specified
queue (default queue).
Restores the default weight of 20.
OL-16184-01, Cisco MDS SAN-OS Release 3.x
56-3 to 56-11).