Data Center Levels – What Are they?
Data center tiers, also referred to as data center levels (these terms are interchangeable), are a method of categorizing data centers based on their infrastructure’s availability, redundancy, and reliability. This classification system clearly explains a data center’s anticipated performance and uptime. Organizations such as the Uptime Institute or the Telecommunications Industry Association (TIA) are usually responsible for defining and outlining these tiers.
Understanding Hosting Tiers and Data Center Infrastructure
When discussing data hosting tiers, we are referring to the various levels or types of hosting services providers offer. These levels describe the resources, features, and support the hosting service provides. Hosting tiers are designed to clarify the level of service and infrastructure reliability offered by a hosting provider. Each hosting service level — such as shared, VPS, dedicated, and cloud — has its own set of characteristics and capabilities, categorized into tiers.
The reliability and performance of hosting tiers are often influenced by the underlying data center infrastructure supporting them. Data center infrastructure is also classified into tiers (Tier 1, Tier 2, Tier 3, Tier 4), where generally, the higher the tier, the greater the availability.

The Four Data Center Tiers
Data center tiers are a method for standardizing the classification of data center facilities based on their security, redundancy, and availability levels. They are an effective way to communicate essential details about data center facilities quickly.
The Uptime Institute sets the standards for data center levels and assigns tiers to facilities based on various factors, some of which require public disclosure. Below is a breakdown of each tier and its requirements:
Tier One
- Basic site infrastructure with expected availability of 99.671%
- Single non-redundant distribution path with non-redundant capacity components
- Planned work and outages will require most or all of the site to be shut down
- Power and cooling systems are not redundant, making maintenance challenging without downtime
Tier Two
- Meets or exceeds all Tier 1 requirements
- Redundant site infrastructure capacity and single, non-redundant distribution path with expected availability of 99.741%
- Redundancy in power and cooling systems reduces downtime during planned maintenance

Tier Three
- Meets or exceeds all Tier 1 and Tier 2 requirements
- Concurrently maintainable site infrastructure with an expected availability of 99.982%
- Multiple independent distribution paths, but only one path required
- The equipment is dual-powered & fully compatible with the topology of the site’s architecture
- Maintenance on power and cooling systems can be performed without disrupting operations
Tier Four
- Meets or exceeds all Tier 1, Tier 2, and Tier 3 requirements
- Fault-tolerant site infrastructure with electrical power storage and distribution facilities and an expected availability of 99.995%
- Fault-tolerant systems include multiple, independent, physically isolated components for power and cooling
- Independently powered cooling and power systems ensure continuous operation, even after an infrastructure failure
- Maintenance can be performed on any component without impacting performance or availability
Next Steps in Choosing the Right Data Center Levels
Each data center tier offers different performance levels, scalability, control, and cost. Choosing the right data center level depends on factors such as the size of your website or application, expected traffic volume, budget, and specific technical requirements.
When selecting a hosting level, you will need to assess your needs carefully and consider factors like uptime guarantees, support quality, and additional features (like security and backup options).
Contact us today with your questions about the cloud or cloud enablement services. Our experts are always happy to discuss your needs.
