Cisco Cisco MDS 9500 Series Supervisor-2 Module White Paper
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White Paper
Intelligent Traffic Services with
the Cisco MDS 9000 Family Modules
the Cisco MDS 9000 Family Modules
The second-generation Cisco
®
MDS 9000 Family modules offer extensive tools for traffic engineering.
INTRODUCTION
As storage networks continue to mature and grow in scale, the level of service provided by those networks must scale as well. The demands of
today’s high-performance storage subsystems and the growing number of servers in the data center require a storage area network (SAN) that can
provide robust performance and on-demand flexibility while still maintaining an attractive cost structure. Efficient utilization of network bandwidth
is crucial in building a large-scale enterprise data center SAN. Even as 4-Gbps and 10-Gbps Fibre Channel interfaces become available, most
servers, storage subsystems, and applications continue to run at 1 Gbps or 2 Gbps. Because of this fact, it is very important to be able to effectively
allocate the network bandwidth to accommodate actual I/O throughput at each interface dynamically. Cisco MDS 9000 Family intelligent
oversubscription technology, using a flexible crossbar-based modular design, allows for a mix of price and performance to meet any SAN
requirements.
OVERSUBSCRIPTION
With the introduction of the Cisco MDS 9000 Family platform, Cisco Systems
®
changed the way that SANs were designed and deployed. One of the
most compelling design options that it offers is the choice between a full-rate module and an oversubscribed module. This choice allows the best mix
of performance (storage, tape, and Inter-Switch Links [ISLs]) and price per port (large number of servers). Because 95 percent of Cisco MDS
customers purchase oversubscribed modules, these modules have pushed the cost of deploying a SAN down while maintaining critical
application performance.
One characteristic that makes oversubscribed modules ideal for most data center servers is their ability to respond to line-rate bursts of data. The
first-generation 32-port module (DS-X9032) for the Cisco MDS 9000 Family shared 2.5 Gbps of bandwidth per four-port group. This allowed any
device to burst at high data rates and still have performance available for the other three ports in the group (Figure 1). The 32-port module also
instituted a round robin mechanism that prevents any one device from taking all the bandwidth from another device. This allows for complete
fairness if the aggregate of the four devices exceeds the available 2.5 Gbps of bandwidth available.
Figure 1. Data Burst and Fairness Capability in Oversubscribed Modules