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White Paper

Data Center Top-of-Rack Architecture Design
What You Will Learn
Forward-looking IT departments are preparing their data centers for the future by integrating support for 10 Gigabit Ethernet and a unified network fabric into their switching and cabling strategies. Since the typical data center lifecycle is 10 to 15 years, cabling architectures have a tremendous effect on the datacenter’s ability to adapt to network architecture changes, evolving bandwidth needs, and technology moves, additions, and changes. Cabling architectures, if not chosen correctly, could force an early replacement of the cabling infrastructure to meet connectivity requirements as the network and computer technologies evolve. Today’s data centers deploy a variety of cabling models and architectures.With the migration from Gigabit Ethernet to 10 Gigabit Ethernet, cabling and network switching architectures are being reevaluated to help ensure a cost-effective and smooth data center transition. The choice of cabling architecture will affect throughput, expandability, sustainability, optimum density, energy management, total cost of ownership (TCO) and return on investment (ROI). Anticipatinggrowth and technological changes can be difficult, but the data center should be able to respond to growth and changes in equipment, standards, and demands while remaining manageable and reliable. This document examines the use of the top-of-rack (ToR) cabling and switching model for nextgeneration data center infrastructure. It explores current 10 Gigabit Ethernet cabling choices and provides asolution architecture based on ToR to address architectural challenges. Data center managers and facilities administrators will choose cabling architectures based on various factors. The ToR model offers a clear access-layer migration path to an optimized high-bandwidth network and cabling facilities architecture that features low capital and operating expenses and supports a “rack-and-roll”computer deployment model that increases business agility. The data center’s access layer, or equipment distribution area (EDA), presents the biggest challenge to managers as they choose a cabling architecture to support data center computer connectivity needs. The ToR network architecture and cabling model proposes the use of fiber as the backbone cabling to the rack, with copper and fiber media forserver connectivity at the rack level.

Introduction
The data center landscape is changing rapidly. IT departments building new data centers, expanding existing data center footprints, or updating racks of equipment all have to design a cabling and switching architecture that supports rapid change and mobility and accommodate transitions to 10, 40, and 100 Gigabit Ethernet over time. The mainfactors that IT departments must address include the following:
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Modularity and flexibility is of paramount importance: The need to rapidly deploy new applications and easily scale existing ones has caused server-at-a-time deployment to give way to a rack-at-a-time model. Many IT departments are ordering preconfigured racks of equipment with integrated cabling and switching and as many as 96servers per rack. The time required to commission new racks and decommission old ones is now a matter of hours rather than days or weeks. Because different racks have different I/O requirements,

© 2009 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.

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data center switching and cabling strategies must support a wide variety ofconnectivity requirements at any rack position.
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Bandwidth requirements are increasing: Today’s powerful multisocket, multicore servers, blade systems, and integrated server and rack systems, often running virtualization software, are running at higher utilization levels and impose higher bandwidth demands. Some server racks are populated with servers requiring between five and seven Gigabit...