Data Center Tiers: What Tier II+ Means and Why It Matters

A data center’s tier isn’t a marketing sticker — it describes what happens to your server when power, cooling or connectivity fails.

What the classification describes

Tiers describe the level of redundancy in the facility’s infrastructure: power, cooling and network. The higher the tier, the fewer single points of failure that could take your equipment down.

• Tier I — basic infrastructure with no redundancy. Any maintenance requires a shutdown.
• Tier II — redundancy for key components: uninterruptible power supplies, a generator, spare cooling capacity.
• Tier III — any component can be serviced without shutting down equipment.
• Tier IV — fault tolerance: the system survives the failure of any component.

What Tier II+ means

It’s a tier with redundancy for key power and cooling elements — plus selected features typical of a higher tier. In practice: if city power goes out, UPS units pick up the load, and during a prolonged outage a diesel generator starts; if one provider fails, traffic is rerouted through another via BGP.

What to look at beyond the tier

• Is there a diesel generator, and how many hours of fuel are on hand?
• How is cooling organized, and what happens at the summer heat peak?
• How many carriers are connected to the facility?
• How is access to the server room controlled?
• What availability level is written into the contract?

How we do it

Our facility in Tashkent meets Tier II+: uninterruptible power supplies and a diesel generator, climate control, security and restricted access to the server room, and BGP connectivity with multiple carriers. Service availability is guaranteed in the contract at 99.5%.