What are Data Center Tiers and Data Center Types？

A data center is a facility consisting of one or more buildings that house centralized computing infrastructure, typically servers, storage, and networking equipment.

In this world of apps, big data, and digital everything, you can't stay ahead of your industry without a state-of-the-art computing infrastructure. If you want to keep things in-house, the answer is the data center. Its primary role is to support all the critical business applications and workloads that all organizations use to run their business.

In this article, we will look at the different types of data centers, data center tier classification, and which data center tier is best for your organization to build your own data center.

Types of Data Centers

There are different types of data center facilities, and a single company might use more than one type, depending on workloads and business needs.

Enterprise Data Centers: These are built, owned, and operated by companies and are optimized for their end users. Most often they are housed on the corporate campus.

Managed Services Data Centers: These data centers are managed by a third party (or a managed services provider) on behalf of a company. The company leases the equipment and infrastructure instead of buying it.

Colocation Data Centers: In colocation ("colo") data centers, a company rents space within a data center owned by others and located off company premises. The colocation data center hosts the infrastructure: building, cooling, bandwidth, security, etc., while the company provides and manages the components, including servers, storage, and firewalls.

Cloud Data Centers: In this off-premises form of data center, data and applications are hosted by a cloud services provider such as Amazon Web Services (AWS), Microsoft (Azure), or IBM Cloud or other public cloud providers.

Data Center Tier Classification

While these data center types cater to various needs, their performance and reliability can be further defined by the Tier Classification System. The Tier Classification System, established by the Uptime Institute in 2005, provides a consistent, globally recognized standard for data center performance. It defines four distinct levels of redundancy—Tier 1, Tier 2, Tier 3, and Tier 4—each with specific criteria related to redundancy, uptime guarantees, staff expertise, maintenance protocols, and more. This system ensures clear and objective benchmarks for evaluating data center reliability and performance.

Tier 1 Data Center

A Tier 1 data center offers no redundancy for critical systems. It requires basic infrastructure, including a UPS, designated IT space, cooling equipment that operates outside office hours, and a backup generator. It uses a single distribution path for power and cooling, which means it’s vulnerable to disruptions, including maintenance.

With limited resilience, a Tier 1 data center guarantees:

No redundancy

99.671% uptime per year

Maximum of 28.8 hours of downtime per year

Tier 2 Data Center

Build on the requirements of Tier I by adding some redundant components. This partial redundancy increases reliability, ensuring 99.741% uptime annually, or 22 hours of downtime per year. However, these data centers still rely on a single distribution path for power and cooling, meaning they remain vulnerable to unexpected disruptions.

A Tier 2 data center guarantees:

Some cooling and power redundancies

99.741% uptime per year

No more than 22 hours of downtime per year

Tier 3 Data Center

A Tier 3 data center offers N+1 redundancy and multiple power and cooling paths for better reliability. N+1 means it has extra components for backup, so if one fails, performance isn’t affected. It also allows for concurrent maintainability, meaning maintenance can be done without disrupting services.

While more reliable than Tier I and II, it’s not fully fault-tolerant and still at risk of downtime during unexpected events, especially during maintenance when backup components are in use.

A Tier 3 data center guarantees:

N+1

redundancy

Not fully fault-tolerant

99.982% uptime

≤1.6 hours of downtime per year

Tier 4 Data Center

Tier 4 data centers are the most advanced, offering full fault tolerance with 2N (or N+N) redundancy. Every critical component is duplicated, and there are multiple distribution paths, ensuring the facility can handle both planned and unplanned events, like maintenance or unexpected failures. If a disruption occurs, the backup systems take over seamlessly.

For added protection, a 2N+1 model may be used, providing double the capacity (2N) plus an extra backup component (+1) in case of additional failures. This ensures maximum reliability, so issues are likely unnoticed by users.

A Tier 4 data center guarantees:

2N or 2N+1

redundancy

Fault tolerant; no single point of failure

99.995% uptime per year

≤26.3 minutes of downtime per year

Which Data Center Tier Is Best for Your Business?

The increasing demand for high availability is pushing organizations to rely on third-party data centers. The uptime and performance these facilities provide help businesses grow without worrying about system failures or natural disasters disrupting their operations. When evaluating your reliability needs, the Tier Classification System can guide you in choosing the right data center tier level that balances your risk tolerance and budget.

	Uptime per year	Downtime per year	Redundancy	Cost	Traditional Customer
Tier I	99.671%	<28.8 hours	None	$	Small businesses Start-ups Businesses with simple requirements
Tier II	99.741%	<22 hours	Partial power and cooling redundancy	$$	SMB
Tier III	99.982%	<1.6 hours	N+1 fault tolerance	$$$	Growing businesses Large businesses
Tier IV	99.995%	<26.3 minutes	2N or 2N+1 fully fault-tolerant	$$$$	Government entities Large enterprises Businesses with international reach

FS Data Center Products and Services

FS provides enterprises with high-performance, low-latency data center solutions that are custom-tailored to meet data storage, processing, and management needs. In addition, FS offers a comprehensive range of networking devices as well as technical services to transform enterprises into the new data center era.