> # Configuration Examples for QoS

> This section describes a configuration example for the application

> Both the OLTP server and the backup server are accessing the disk. The backup server is writing large amounts of data to the disk. This data does not require specific service guarantees. The volumes of data generated by the OLTP server to the disk are comparatively much lower but this traffic requires faster response because transaction processing is a low latency application.

> The point of congestion is the link between Switch 2 and the disk, for traffic from the switch to the disk. The return path is largely uncongested as there is little backup traffic on this path.

> Service differentiation is needed at Switch 2 to prioritize the OLTP-server-to-disk traffic higher than the backup-server-to-disk traffic.

> ## Detailed Steps

> To configure traffic prioritization for the example application, follow these steps:

> 1. Create the class maps.
> 2. Create the policy map.
> 3. Assign the service policy.
> 4. Assign the weights for the DWRR queues.
> 5. Repeat Step 1 through Step 4 on Switch 1 to address forward path congestion at both switches.

> Congestion could occur anywhere in the example configuration. To address congestion of the return path at both switches, you need to create two more class maps and include them in the policy map as follows:

> 1. Create two more class maps.
> 2. Assign the class maps to the policy map.
> 3. Repeat Step 1 through Step 2 on Switch 1 to address return path congestion at both switches.

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