Configuring Data Traffic - Cisco DS-C9216I-K9 Configuration Manual

Data Traffic
Figure 27-2
OLTP server
Backup server
In Figure
classification (class map) and marking (policy map). Similarly, the backup traffic is marked with a Low
priority level. The traffic is sent to the corresponding priority queue within a Virtual Output Queue
(VOQ).
A Deficit Weighted Round Robin (DWRR) scheduler configured in the first switch ensures that high
priority traffic is treated better than low priority traffic. For example, DWRR weights of 70:20:10 implies
that the high priority queue is serviced at 7 times the rate of the low priority queue. This guarantees lower
delays and higher bandwidths to high priority traffic if congestion sets in. A similar configuration in the
second switch ensures the same traffic treatment in the other direction.
If the ISL is congested when the OLTP server sends a request, the request is queued in the high priority
queue and is serviced almost immediately as the high priority queue is not congested. The scheduler
assigns it priority over the backup traffic in the low priority queue.
When the high priority queue does not have traffic flowing through, the low priority queue uses all the
bandwidth and is not restricted to the configured value.
A similar occurrence in Switch 2 sends a response to the transaction request. The round trip delay
experienced by the OLTP server is independent of the volume of low priority traffic or the ISL
congestion. The backup traffic uses the available ISL bandwidth when it is not used by the OLTP traffic.
To achieve this traffic differentiation, be sure to enable FCC.

Configuring Data Traffic

To configure QoS, follow these steps.
Enable the QoS feature.
Step 1
Create and define class maps.
Step 2
Define service policies.
Step 3
Cisco MDS 9000 Fabric Manager Switch Configuration Guide
27-4
Prioritizing Data Traffic
VOQ(s)
Absolute
High
Medium
Low
Switch 1
27-2, the OLTP traffic arriving at Switch 1 is marked with a High priority level of through
Chapter 27 Configuring Traffic Management
Disk
FC FC
Congestion
VOQ(s)
Absolute
High
Medium
Low
Switch 2
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