What are Data Centre Tiers?

30th August 2016

In its simplest form, a data centre is a collection of servers which are interconnected and accessible to users.  A small data centre might be no more than a single rack within an office, while a large corporate data centre might be a large warehouse with thousands of individual machines operating together. The server space in a data centre might be allocated to a single business, or multiple entities, and the machines may act as individual dedicated servers with a single user, or run a cloud operating system that ties them together.  Data centres are characterised based on a number of different features which group them into tiers.  If you’re in the process of securing server resource, one of the key questions that you will ask is “what are data centre tiers, and what do they mean for my business.

Who Defines Data Centre Tiers?

The global trade body that governs the data centre industry is the Telecoms Industry Association, and in the UK, the Federation of Communication Services fulfils a similar role.  These bodies have agreed definitions for the different tiers of data centre and provided a hosting company is able to meet the various criteria, they are able to market their data centres as being appropriate to certain tiers.

Traditional data centres fit into groups from Tier I to Tier IV, and the standards for acceptance of these levels translate into cloud services.  As such, a cloud service such as Microsoft Azure or Amazon EC2 may be described as being equivalent to Tier X when sold to a consumer.

Criteria for Data Centre Tiers

There are 5 criteria under which different data centre tiers are defined.  These are as follows:

  • Availability
  • Redundancy
  • Power & Cooling
  • Impact of Planned Outages
  • Impact of unplanned outages

As you go up the list of Tiers from I to IV, there are ever more stringent requirements in place to meet the required standards.

Data Centre Availability

Availability refers to the percentage of time that the operator guarantees that the datacentre will be accessible and that information can be accessed.  The lowest level of guaranteed availability is 99.67%.  While this seems very high, it allows for almost 29 hours of downtime over the course of a year – just over one day.  At the highest level Tier IV, the allowable downtime in a 12-month period is just over 0.4 hours – about 26 minutes.  For web based businesses, lost time means lost revenue.

Data Centre Redundancy

Data centre redundancy refers to the level of support that is in place in the event of a planned outage.  Redundant capacity means that if a machine fails, another machine is available to take its place.  In a Tier I data centre, there is minimal redundancy – i.e. no guarantee of a backup.  If capacity is available, then there may be a machine to fall back onto, but it is not a requirement.  At Tier IV, you would expect multiple redundancy options which may include alternative machines in the same data centre, or even a backup data centre that can be switched to in an emergency.

Data Centre Power and Cooling

A reliable source of power for a data centre is essential to prevent outages.  Tier I and Tier II data centres have no requirement for alternative sources of power and cooling, so in the event of a blackout in the area, all machines will shut down.  With multiple sources of backup power, the risk of outage is significantly reduced.  Larger data centres will often have their own power supplies on site in the form of generators to ensure consistent up time in the event of wider issues.

Impact of Planned / Unplanned Outages

From time to time, all servers will need to be re-booted.  This may be due to software being updated, or may be due to components being switched for reliability reasons.  The impact of these outages is governed by the level of redundant capacity in the data centre, and access to an uninterrupted supply of power.

The nature of Tier I data centres means that there will be disruption to services in the event of either an unplanned or planned outage.  Most companies will plan outages during times of low demand such as the middle of the night.

Comparison between Traditional Data Centres and Cloud Data Centres

Cloud services such as Microsoft Azure work differently to a traditional data centre, as the individual servers are replaced by virtual machines that run across multiple physical servers.  This usually means that redundancy is built in, and also the impact of outages is minimised as it is rare that all machines will be impacted by an event.

For larger cloud providers, where multiple international data centres are available to act as back up, interruptions are minimised.  Cloud Services such as Azure typically offer a level of service that’s equivalent to Tier III although the actual level will be dependent on the specification that you choose.  For example, if you only have a single Virtual Machine and opt out of some additional services, you may have less protection than you would with a Tier II data centre.

Enhanced Cloud Services

In addition to the standard cloud technology, it is possible to configure services to reach even higher levels of robustness.  Our Azure Managed Services suite, Cloud Control configures multiple virtual machines in your network to enable us to provide a level of security and reliability that’s slightly better than a Tier IV data centre at a much reduced cost.

What are Data Centre Tiers?

The following table shows the information outlined above for comparison.

For more information about how igroup can provide your organisation with a Tier IV+ Data Centre at a fraction of the cost you’d expect, please contact a member of our team today on 0207 099 0632, or visit our Azure information pages to discover more about your options or to request a quote, and we’ll be happy to help you.

 

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