Colocation: how to choose the right datacenter (Tier, redundancy, PUE)

Hosting your servers in a datacenter — colocation — means entrusting the physical foundation of your IT (power, cooling, security, network) to a site engineered never to stop. But you still have to pick the right site: not all datacenters are equal, and the differences show up as availability on the day something fails.

Understanding "Tier" levels

The Tier classification (I to IV, defined by the Uptime Institute) summarises the infrastructure's redundancy and therefore its expected availability:

• Tier I / II: partial redundancy, maintenance requiring downtime. Suitable for non-critical uses.
• Tier III: concurrently maintainable, N+1 redundancy. This is the standard for most professional infrastructures.
• Tier IV: fault tolerant, dual active path for power and cooling. Reserved for the most critical uses.

Power and cooling: N+1 redundancy

The heart of a datacenter is its ability to power and cool your equipment continuously. Look at electrical redundancy (dual feed, UPS, generators and their fuel autonomy) and cooling (N+1 units, hot/cold aisle containment). The PUE (Power Usage Effectiveness) metric measures energy efficiency: the closer to 1, the less energy is wasted — a good PUE is both greener and cheaper.

Physical security and compliance

A serious datacenter strictly controls access (badges, biometrics, mantraps, 24/7 CCTV), detects and suppresses fire, and documents everything. Certifications (ISO 27001 for information security, HDS for health data in France) attest to a level of rigour verified by a third party.

Connectivity: the forgotten criterion

A perfectly powered but poorly connected server is still useless. A good hosting site is carrier-neutral, close to exchange points, and lets you choose your transit. This is where hosting with a network operator makes all the difference: connectivity isn't an add-on, it's the core business.

The checklist before you sign

• Availability: which Tier, which commitments (SLA) and what penalties?
• Redundancy: power and cooling at least N+1?
• Security: access control, certifications, intervention procedures.
• Connectivity: choice of operators, capacity, DDoS protection available.
• Operations: is there 24/7 support and remote hands?

At Connect-IX, our hosting offering relies on top-tier datacenters and, above all, on our own network: your infrastructure natively benefits from quality IP transit and integrated DDoS protection. And if you'd rather delegate operations, our managed IT takes over.