Cisco Cisco MDS 9500 Series Supervisor-2 Module Libro blanco

Important notices, privacy statements, and trademarks of Cisco Systems, Inc. can be found on cisco.com.

Page 3 of 6

Figure 2. Bandwidth Allocation in a Six-Port Port Group

Bandwidth Allocation also allows ISLs to be used on an oversubscribed module. Because full line rate can be reserved for any given port, a port

within the port group can be set to full 4-Gbps speed, guaranteeing full performance for saturated ISLs in the network. This feature makes a chassis

with all oversubscribed modules a viable configuration in many data centers.

QUALITY OF SERVICE

The adoption of a service provider model within the enterprise data center has added the requirement of tiered service levels among storage arrays.

Adding tiers enables the possibility of adding service-level agreements (SLAs). An important component to an SLA is the priority of one application

or storage service over another. If a true quality-of-service (QoS) mechanism is enabled in the Cisco MDS 9000 Family module, applications can be

distinguished by traffic priority.

The flexibility of QoS on the Cisco MDS 9000 Family module enables a simple mechanism to prioritize applications both within a switch and across

the entire network. Using the proven mechanism of Deficit Weighted Round Robin (DWRR), users can determine not only application priority but

also the weight of that priority. The Cisco MDS 9000 Family supports four QoS queues, the first of which is absolute priority. The remaining three

queues are user definable (see Figure 3).

Figure 3. Fibre Channel Port Ingress QoS

Each of the three user-definable queues maintains a separate weight, with the total weight of the three queues equaling 100 percent. Although the

fourth queue (absolute priority) is used for network control traffic such as Fabric Shortest Path First (FSPF) updates or zoning changes, the three

user-definable queues are used for end devices. To help ensure simple management and easy operation, QoS is enabled on a per-zone basis. This

simple method allows for easy QoS configuration either when a zone is created or when QoS is enabled.