Introduction to Network Datacenters

Google Builds Computing Center In Oregon (2006)
Google Builds Computing Center In Oregon (2006). Getty Images North America

A datacenter is a facility specially constructed to centrally house computer hardware, storage and network connectivity equipment. Some datacenters connect large numbers of servers to the public Internet while others support corporate intranets or other private business purposes.

How Many Datacenters Exist?

Industry firms like International Data Corporation (IDC) estimate that millions of datacenters exist worldwide, including roughly 3 million in the United States alone.

Such estimates tend to include many small sites that may not be dedicated buildings.

How Big Are Datacenters?

People often associate datacenters with huge warehouse-style buildings. The very largest centers in the world span 1+ million square feet (roughly 93,000+ square meters). More typical centers range in size between 1,000 and 50,000 square feet.

See also - The World's Most Interesting Datacenters

Types of Datacenters

Datacenters can be categorized according to their purpose. Three basic kinds exist:

  1. Dedicated
  2. Colocated
  3. Public “cloud”

Dedicated centers are owned and operated by organizations for their own private uses. Many belong to corporations running Web services businesses and also ISPs. Others may be used by research and academic institutions. Large multinational corporations like Google and Facebook maintain a group of datacenters spread across the world, but the majority of businesses with dedicated centers only have one.

Smaller businesses often house their central network equipment in one or more server rooms that may informally be called datacenters, even though these are rooms within larger multi-purpose buildings.

Colocation (sometimes called colo) centers allow multiple customers (sometimes called tenants) to rent floor space in the facility where they can land their own hardware.

Hundreds of colocation providers operate within the United States. These providers supply power, cooling, and Internet backbone connectivity plus also often also sell management and other support services to their collocated customers.

Public centers enable their customers to share third-party virtual and physical hardware resources that may be spread across multiple locations. These centers traditionally offered Web hosting services and now increasingly support cloud storage and other cloud computing services.

Two industry groups have separately defined standards for classifying the different kinds of datacenters into tiers according to their operational capabilities. An organization called the Uptime Institute defines these four tiers:

  • Tier 1: A maximum of 28.8 hours of downtime per year, with no redundant power or cooling/ventilation systems.
  • Tier 2: A maximum of 22 hours of downtime per year, with partially redundant power and cooling.
  • Tier 3: A maximum of 1.6 hours of downtime per year, with more fault tolerance
  • Tier 4: A maximum of 26.3 minutes of downtime per year, with fully redundant components.

The Telecommunications Industry Association (TIA) developed a similar standard called ANSI/TIA-942, also with four tiers, covering centers ranging from very small businesses to the largest enterprises.

Datacenter Space Planning

Establishing a new datacenter involves a long term (often multi-year) effort of planning and design. First, planners must choose a suitable site location. They must also estimate physical space and network bandwidth needs.

Floor space in data centers tends to be scarce. Even in large centers, the ability to scale and fit more hardware into a given area becomes a key business advantage. (Colocation businesses, for example, can sell more services to a larger customer base with lower cost.) The amount of space usable for servers reduces significantly after walkways and operations areas are factored into floorplans. Finally, organizations also need to plan a new datacenter with some reserve space to allow for future growth.

Datacenter equipment including so-called blade servers installs into rack enclosures. Over years the industry eventually standardized on racks 19 inches (482.6 mm) wide designed to fit hardware of fixed heights, specifically, multiples of 1.752 inches (44.5 mm, a number often abbreviated as ‘U’). Rack heights of 42U (about 73.5 inches) became a de-facto standard as well. Nowadays, however, larger racks such as those 21 inches wide and 45U or 48U high also can be found in centers due to ongoing pressure to squeeze more devices into available space.

Power Utilization in Data Centers

Power requirements for datacenters vary depending on their size. Center designs normally specify power needs as either watts per square foot (W/sf) or watts per rack. Because a data center utilizes large numbers of servers, its total power utilization can be enormous (as much as some small towns!), with typical power delivery demands of at least 3-5 kW per rack. A significant fraction of the total is required simply for cooling and ventilation systems to keep the densely packed hardware from overheating.

Managing a Datacenter

Business enterprises set up datacenters in part because they require high availability systems and services such as e-commerce support. The top tier (Tier 4 as defined by the Uptime Institute) global centers can literally afford only minutes of downtime over the span of a year, more than 99.99% (so-called four-nines) availability, while even the lowest Tier 1 centers used by small businesses still require more than 99% (“two-nines”) uptime. Battery (UPS) and generator backup systems are essential components in these environments, as are hot-swappable hardware (field replaceable units) and use of redundant network links in some cases.

Managing the high volume of data traffic generated by a datacenter becomes increasingly challenging as it grows. Sudden spikes in traffic demand can quickly overload portions of the internal network.

Network security considerations also take on a critical importance in data centers, where the high concentration of business data and contracts presents an appealing target for hackers and thieves. Relatively few people are needed to operate a well-designed datacenter, but some of those kept on staff are there specifically to guard building perimeters and entrances.

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