I N D I A P R I V A T E L I M I T E D
LOGICAL TOPOLOGIES FOR DATA CENTER
Data centers contain many network transmission protocols for communication between electronic equipment. Ethernet and Fibre Channel are the dominant networks, with Ethernet providing a local area network (LAN) between users and computing infrastructure while Fibre Channel provides connections between servers and storage to create a storage area network (SAN). To design a structured cabling system for a data center, the designer should understand the different protocols that are used in each area of the data center.
> LAN Protocols
> SAN Protocols
While standards help guide the data center physical infrastructure, the data center logical infrastructure does not have a standards body helping with design. Logical architectures vary based on customer preference and are also guided by the electronics manufacturers. Though a standard does not exist, there are some common architecture best practices that can be followed. Most logical architectures can be broken into four layers :
TIER RATINGS FOR DATA CENTERS
Additional considerations when planning a data center infrastructure include redundancy and reliability. TIA-942 describes redundancy using four tiers to distinguish between varying levels of availability of the data center infrastructure. The tiers used by this standard correspond to industry tier ratings for data centers, as defined by the Uptime Institute. The tiers are defined as Tier I, II, III and IV, where a higher tier rating corresponds to increased availability. Tier ratings are specified for various portions of the data center infrastructure, including telecommunications systems architectural and structural systems, electrical systems and mechanical systems. Each system can have a different tier rating, however; the overall data center tier rating is equal to the lowest of the ratings across the infrastructure.
APPLICABLE STANDARD : TIA-942
TIA-942, Telecommunications Infrastructure Standards for Data Centers, was released in April 2005. The purpose of this standard is to provide information on the factors that should be considered when planning and preparing the installation of a data center or computer room. TIA-942 combines within a single document all of the information specific to data center applications. This standard defines the telecommunications spaces, infrastructure components and requirements for each within the data center. Additionally, the standard includes guidance as to recommended topologies, cabling distances, building infrastructure requirements, labeling and administration, and redundancy.
DATA CENTER SPACES AND INFRASTRUCTURE
The main elements of a data center, defined by TIA-942, are :
- Entrance room (ER)
- Main distribution area (MDA)
- Horizontal distribution area (HDA)
- Equipment distribution area (EDA)
- Telecommunications room (TR)
The components of the cabling infrastructure, as defined by TIA-942, are as follows :
- Horizontal cabling
- Backbone cabling
- Cross-connect in the ER or MDA
- Main cross-connect in the MDA
- Horizontal cross-connect in the TR, HDA, MDA
- Zone outlet or consolidation point in the ZDA
- Outlet in the EDA
In a data center, including HDAs, the maximum distance allowed for horizontal cabling is 90 m, independent of media type. With patch cords, the maximum channel distance allowed is 100 m, assuming 5 m of patch cord at each end of the channel for connection to end equipment. When a ZDA is used, horizontal cabling distances for copper may need to be reduced. Depending on the type and size of the data center, the HDA may be collapsed back to the MDA. This is a typical design for enterprise data centers. In this scenario, the cabling from the MDA to the EDA, with or without a ZDA, is considered horizontal cabling. In a collapsed design, horizontal cabling is limited to 300 m for optical fiber and 90 m for copper. TIA-942 defines the maximum distance for backbone cabling as being application and media dependent.
There are two types of environments in the data center: local area networks (LANs) and storage area networks (SANs). A LAN is a network linking multiple devices in a single geographical location. Typical LAN speeds are 1 Gb or 10 Gb Ethernet. A SAN is an area in the network linking servers to storage equipment, which introduces the flexibility of networking to servers and storage. Speeds are typically 2G, 4G, 8G or 10G Fibre Channel.
When designing a data center, several factors should be taken into consideration, including standards compliance. TIA-942, Telecommunications Infrastructure Standard for Data Center, details several of the factors that should be considered when designing a data center. When implementing a structured cabling solution, the standard recommends a star topology architecture to achieve maximum network flexibility. TIA-942 outlines additional factors crucial to data center design, including recognized media, cable types, recommended distances, pathway and space considerations and redundancy. In addition to standards compliance, the need for infrastructure flexibility to accommodate future moves, adds and changes due to growth, new applications, data rates and technology. Advancements in system equipment must be considered.
As data centers face the continued need to expand and grow, the fundamental concerns are constant. Data center infrastructures must provide reliability, flexibility and scalability in order to meet the ever-changing data center network.
> Network Efficiency
> Flexibility and Scalability
A data center, as defined in TIA/EIA-942, Telecommunications Infrastructure Standard for Data Centers, is a building or portion of a building whose primary function is to house a computer room and its support areas. The main functions of a data center are to centralize and consolidate information technology (IT) resources, house network operations, facilitate e-business and to provide uninterrupted service to mission-critical data processing operations.
Data centers can be classified as either enterprise(private) data centers or co-location(co-loc)/ hosting(public) data centers. Enterprise data centers are privately owned and operated by private corporate, institutional or government entities. Enterprise data centers support internal data transactions and processing, as well as Web Services and are supported and managed by internal IT support. Co-loc data centers are owned and operated by telcos or unregulated competitive service providers and offer outsourced IT services. Services that data centers typically provide include Internet access, application or web hosting, content distribution, file storage and backup, database management, fail-safe power, HVAC controls, security and high-performance cabling infrastructure.