What is Data Center?

The data center is home to the computational power, storage, and applications necessary to support an enterprise business. The data center infrastructure is central to the IT architecture, from which all content is sourced or passes through. Proper planning of the data center infrastructure design is critical, and performance, resiliency, and scalability need to be carefully considered.

Another important aspect of the data center design is flexibility in quickly deploying and supporting new services. Designing a flexible architecture that has the ability to support new applications in a short time frame can result in a significant competitive advantage. Such a design requires solid initial planning and thoughtful consideration in the areas of port density, access layer uplink bandwidth, true server capacity, and oversubscription, to name just a few.

The data center network design is based on a proven layered approach, which has been tested and improved over the past several years in some of the largest data center implementations in the world. The layered approach is the basic foundation of the data center design that seeks to improve scalability, performance, flexibility, resiliency, and maintenance.

The layers of the data center design are the core, aggregation, and access layers. These layers are briefly described as follows:
Core layer — provides the high-speed packet switching backplane for all flows going in and out of the data center. The core layer provides connectivity to multiple aggregation modules and provides a resilient Layer 3 routed fabric with no single point of failure.

Aggregation layer — Provide important functions, such as service module integration, Layer 2 domain definitions, spanning tree processing, and default gateway redundancy. Server-to-server multi-tier traffic flows through the aggregation layer and can use services, such as firewall and server load balancing, to optimize and secure applications.

Access layer — where the servers physically attach to the network. The server components consist of 1RU servers, blade servers with integral switches, blade servers with pass-through cabling, clustered servers, and mainframes with OSA adapters. The access layer network infrastructure consists of modular switches, fixed configuration 1 or 2RU switches, and integral blade server switches.

Design Models
Multi-Tier Model
The multi-tier data center model is dominated by HTTP-based applications in a multi-tier approach. The multi-tier approach includes web, application, and database tiers of servers. Today, most web-based applications are built as multi-tier applications. The multi-tier model uses software that runs as separate processes on the same machine using inter process communication (IPC), or on different machines with communications over the network. Typically, the following three tiers are used: 
  • Web-server
  • Application
  • Database
Multi-tier server farms built with processes running on separate machines can provide improved resiliency and security.

Server Cluster Model
In the modern data center environment, clusters of servers are used for many purposes, including high availability, load balancing, and increased computational power. This guide focuses on the high performance form of clusters, which includes many forms. All clusters have the common goal of combining multiple CPUs to appear as a unified high performance system using special software and high-speed network interconnects. Server clusters have historically been associated with university research, scientific laboratories, and military research for unique applications, such as the following:
  • Meteorology (weather simulation)
  • Seismology (seismic analysis)
  • Military research (weapons, warfare)
Server clusters are now in the enterprise because the benefits of clustering technology are now being applied to a broader range of applications. The following applications in the enterprise are driving this requirement:
  • Financial trending analysis—Real-time bond price analysis and historical trending
  • Film animation—rendering of artist multi-gigabyte files
  • Manufacturing—Automotive design modeling and aerodynamics
  • Search engines—Quick parallel lookup plus content insertion
HPC Cluster Types and Interconnects
In the high performance computing landscape, various HPC cluster types exist and various interconnect technologies are used. The top 500 supercomputer list at www.top500.org provides a fairly comprehensive view of this landscape. The majority of interconnect technologies used today are based on Fast Ethernet and Gigabit Ethernet, but a growing number of specialty interconnects exist, for example including Infiniband and Myrinet. Specialty interconnects such as Infiniband have very low latency and high bandwidth switching characteristics when compared to traditional Ethernet, and leverage built-in support for Remote Direct Memory Access (RDMA). 10GE NICs have also recently emerged that introduce TCP/IP offload engines that provide similar performance to Infiniband.

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