99.99% uptime sounds reassuring, but it still allows 52.56 minutes of downtime each year. That’s roughly 4.38 minutes a month or about 1.01 minutes a week. Compare that to our average uptime of 99.999%, where downtime is less than 6 minutes a year. However, even high uptime percentages still allow for some downtime each year. Here’s a short table to explain this better:
| If Uptime Guarantee Is At | Allowed Downtime (per year) | Downtime (per month) |
| 99% | 3 days 15 hours | 7h 12m |
| 99.9% | 8 hours 45 minutes | 43 minutes |
| 99.99% | 52 minutes 32 seconds | 4 minutes 23 seconds |
| 99.999% (5 Nines Availability) | 5 minutes 15 seconds | 26 seconds |
Let’s look at this commercially. If your business makes £10 per minute revenue through your operations, 52.56 minutes of downtime costs about £525.60 each year. Scale to £100 per minute and the same downtime is costing £5,256, and if you earn £1,000 per minute, it’s costing £52,560.
These examples show why procurement teams and technical leads should demand an SLA uptime of 99.999%. While 0.009% difference may not sound much, it is equivalent to 90% less downtime.
Settling for a 99.99% uptime SLA translates to lost sales, missed support calls and reputational hits.
The SLA Illusion – How AWS, Google & Azure Frame The “Four Nines”
Big cloud providers like AWS, Google Cloud and Azure advertise their business continuity hosting using the “four nines,” but even that uptime only applies if you choose specific setups.
These include multi-AZ, premium plans, or multi-region and follow measurement rules that aren’t usually advertised on the product page. Let’s understand what these providers offer.
A Quick Comparison On How These Providers Publish It
| Provider | Typical SLA headline | What do you have to do to get it? | Allowed downtime / year (approx.) | Notes |
| AWS (EC2 / Compute) | 99.99% for region-level and multi-AZ deployments | Deploy instances across two or more AZs in the same region (or follow region-level SLA rules). | 52.56 minutes / year. | AWS advertises a 99.99% Monthly Uptime for EC2 when deployed across multiple AZs, but single-AZ or single setups have lower guarantees and different terms. |
| Google Cloud (Compute Engine) | One VM gives around 99.9% uptime, maybe 99.95% for some types. If you use more zones, it gets more reliable. | To reach higher SLOs you need specific VM types / tiers and multi-zone deployment or Premium Tier networking. | 99.9% uptime means about 526 minutes of downtime a year. 99.95% means about 263 minutes. | Google calls out different SLAs by VM and network tier. Single-instance SLAs are generally lower than multi-zone setups. |
| Microsoft Azure (Virtual Machines) | One VM gives about 99.9% uptime. Run multiple instances across availability zones and you can reach 99.99%.
| You must deploy 2+ VMs across Availability Zones (or use Availability Sets/Zone-redundant configs) to qualify for higher SLAs. | 99.9% uptime means about 526 minutes of downtime a year. 99.99% means only about 53 minutes. | Azure’s SLA improves only when customers run redundant instances across AZs; single-instance SLAs are lower and many caveats apply. |
The Catch – Three Ways SLAs Can Mislead
Measurement Windows and Averaging
SLAs are commonly calculated over billing cycles (usually monthly). That allows for a significant amount of downtime in one week that’s diluted by perfect uptime the rest of the month. A 30-minute outage in January can be “smoothed out” and barely move the advertised monthly or annual figure. Always ask “how SLA is calculated?” (monthly, quarterly, or annually) and whether your chosen provider publishes raw incident logs you can review.
Exclusions and Fine Prints
Providers routinely exclude scheduled maintenance, force majeure events, and sometimes “partial outages” (degraded service affecting only a subset of users).
Those carve-outs can erase large chunks of real downtime from the SLA math. Read exclusions line-by-line as the uptime guarantee on the product page may not equal the uptime your customers experience.
Credits vs Real Business Loss
SLAs are typically paid back with credits and not with real refunds. They are usually a small percentage of your monthly fee, and are often capped.
Credits rarely cover the cost of lost sales, reputational damage or regulatory fines. When evaluating offers, model the credit against estimated business loss and ask what the provider does to make things right when they break their SLA.
Understanding Uptime vs Availability – The Crucial Difference
“Uptime” and “availability” are used interchangeably in marketing, but they can mean different things in practice.
Uptime is often a raw measurement of a resource being live, whilst availability is a broader measure that can factor in how users experience the service (eg. degraded performance, partial failures, failover success).
That distinction is crucial when you compare SLA uptime numbers. If you’re serious about moving beyond “four nines,” it helps to work with a UK provider that builds resilience into both the stack and the contract.
At BlackBox Hosting we offer UK colocation, dedicated servers and managed hosting designed for predictable availability and rapid recovery. Rather than publishing a headline 99.99% uptime claim, BlackBox show you the architecture and operational practices behind that number.
We offer redundant power feeds, geographically separated network paths, automatic failover, and 24/7 monitoring with human escalation to ensure maximum efficiency. Those are the components that make five nines availability (99.999%) more than a theoretical target.
How To Design For Less Than 52 Minutes’ Downtime
If 52 minutes a year is unacceptable, Blackbox Hosting can design a solution to reduce that exposure. Here’s how we can make it happen:
- Build redundancy across racks and sites so a single hardware or site failure does not take you offline.
- Support multi-site and zone-redundant deployments with tested, automatic failover.
- Design stateless services and replicated session stores so nodes can be replaced without data loss.
- Provide network diversity with dual carrier paths to avoid single-provider outages.
- Automate recovery with codified runbooks and self-healing tooling so common failures resolve without manual intervention.
- Run disaster-recovery rehearsals and chaos tests to validate processes and improve response times.
- Audit third-party dependencies and negotiate measurable SLAs so you are not exposed to opaque vendor risk.
Why Blackbox Hosting Is Different
Working with a specialist provider simplifies the move from marketing percentages to operational reality.
BlackBox Hosting offers UK-focused colocation, dedicated servers and managed hosting that prioritises transparency and practical resilience.
What to expect from BlackBox Hosting:
- UK-based support and local network options, reducing latency for domestic customers and streamlining escalation.
- Architecture guidance that balances cost and resilience (so you don’t pay hyperscaler bills for a problem you can solve through smarter system designs).
- Clear SLAs and incident reporting, take a look at our sample incident reports and the exact SLA measurement rules before you sign.
- Managed options that pair infrastructure with operations (monitoring, runbooks, automated failover), making it easier to aim for sub-10 or sub-5-minute annual downtime without building everything yourself.
BlackBox Hosting Delivers More
At BlackBox Hosting we don’t just publish a headline percentage, we show the engineering, the evidence and the outcomes.
From in-depth client case studies to technical service pages that spell out architecture and SLAs, you can see how resilience is built and measured in practice.
Want proof that the approach works? Take a look at our case studies, for example Touchstone’s implementation that walks through architecture, failover design and real-world results.
With free 30 day trials available on our hosting, request a technical audit and talk to our team. We’ll map your exposure (minutes per year) to concrete architecture and contract changes, then back it up with runbooks, incident reports and measurable SLAs.
Ready to see the difference for your stack? Call us on +44(0)2037407840 to connect with our experts today!
