Data Centre Tiers: When Outage is not an Option

Data centres use a tier system – like a standardised unit of reliability. Learn more about data centre tiers and why they matter to business-critical ops.

Data Centre Tiers: When Outage is not an Option

Here’s a nightmare situation for you: Imagine an entire data centre went offline. Your rack space, unusable. Your Private Cloud, inaccessible. Data in transit? Gone – unless you’ve got a robust business continuity and disaster recovery plan in place.

This is a bad day, by any measure. But we actually saw this happen recently.

A prominent data centre (not one of ours, as we’ll explain) had a power issue. This resulted in all power to the data centre floor being lost. Now, in the data centres we spec for customers, we always look for two, totally redundant power sources – with two redundant paths for mains power, UPSs (uninterruptable power supplies), and generators. These are presented on two separate PDUs (power distribution units), and we connect equipment to both for resilience.

But not here. The mains went off, the UPSs took over as expected, but there was another failure when swapping between the UPSs and generators, which meant they never got chance to take over.. and, there was no redundant second power source. Why not, you might be wondering – this is a pretty standard expectation in modern IT infrastructure, isn’t it?

Well, actually… No. Data centres are not all made equal. Some are purpose-built, some are highly modified, and some are kind of cobbled together. It seems ridiculous that a data centre (and all its customers) could be completely floored by a power outage. But when you look closely at the specs of this particular data centre, the reasons behind the outage becomes more obvious.

In the wake of the incident, we started looking at the specs. It brought up an interesting conversation in our team about data centre tiers and the importance of knowing your data centre’s resilience.

What are the different data centre tiers?

Data centres use a tier system to describe infrastructure in a consistent way – kind of like a standardised unit of reliability. They are there to help you decide whether there is a good enough level of resilience for you. The system is upheld by the Uptime Institute, which issues certification for data centres.

Data centre tiers are ranked from 1 to 4, with tier 4 being the highest.

Higher tiers offer greater redundancy and reliability than lower tiers. Each tier includes the specs of all the tiers below it, plus more.

Here’s a rough outline of what each data centre tier typically offers:

Data Centre Tier 1

A tier 1 data centre has a single path for power and cooling, and no backup components. Expect an uptime of 99.671% per year.

Data Centre Tier 2

A tier 2 data centre also has a single path for power and cooling – but now includes some redundant and backup components, with an expected uptime of 99.741% per year.

Data Centre Tier 3

Tier 3 data centres introduce dual-powered equipment, and multiple uplinks. There are enough backup components to maintain availability during planned maintenance. You can expect an annual uptime of 99.982%.

Data Centre Tier 4

Tier 4 data centres operate at the highest level – with fully fault-tolerant components and independent distribution paths for power and cooling. Uptime can exceed 99.995% per year.

You need to be careful here, because not all data centres make their tier easily known. It’s important to actually check the specs yourself, because that’s the only real way to know if it’ll meet your needs.

The data centre that went offline is marketed as tier 2 – a single path for power. This explains why the power failure was total, but not why a UPS didn’t kick in. Looking closer at the spec sheet, there was not a sufficient level of redundancy for power or for cooling.

This wouldn’t have passed deeserve’s criteria for choosing a data centre. Let’s explain what we look for when choosing a partner to power our rackspace.

Tier 3 or higher

We have found that some data centres don’t show a tier – especially in the USA. So we always check the specifications directly to ensure at least N+1 for power and N+1 for cooling are present for business critical installations.

For instance, the MI6 data centre in Miami hasn’t yet been certified. However, it does offer N+1 on power and N+2 on cooling, which exceeds our criteria and puts it between tier 3 and tier 4.

Both our primary UK data centres, GS2 and Volta, are classed as minimum tier 3.

Long blog story short – if uptime matters to you, you’ve got to check the specs of every prospective data centre – especially around redundancy levels. Not doing so could land you in a nightmare scenario with critical operations at stake!

If you’d rather be getting on with work than figuring out which data centre is right for you, then speak to deeserve’s data centre experts. We can set you up in a world-class data centre, with our managed colocation service.

Or better yet, let us build you a custom Private Cloud – with full IT support, data security, maintenance, and backup as a service – for just one, simple monthly fee. And that includes all your hardware.

Sound good? Let’s talk!

Private Cloud solutions that make business sense

At deeserve, we only offer the best data centres to our customers – and our list of world-class data centres continues to grow. Want to learn more about Private Cloud for your business? Call us on 01509 80 85 86 or send your message to

More services to help

We offer a comprehensive range of IT services to suit all businesses - from "helpdesk"-style IT support to data centre hosting services.

Proactive IT Systems

Established solution partners

  • Microsoft
  • Hp
  • WatchGuard
  • cisco.

Want to work with us?

We are driven by creating experiences that deliver
results for your business and for your customers.
Or just email on