VPS providers often advertise uptime guarantees, but understanding what these actually promise (and don't) matters for realistic reliability planning. This guide explains SLA terminology and its practical implications.
What an SLA Actually Is
A Service Level Agreement is a contractual commitment defining an expected service level (commonly uptime percentage) and typically some form of remedy (usually service credits, not full compensation for business impact) if that level isn't met.
Common Uptime Percentages and What They Mean in Practice
| SLA | Allowed Downtime per Month | Allowed Downtime per Year |
|---|---|---|
| 99% | ~7.3 hours | ~3.65 days |
| 99.9% | ~43 minutes | ~8.76 hours |
| 99.95% | ~22 minutes | ~4.38 hours |
| 99.99% | ~4.3 minutes | ~52.6 minutes |
What SLAs Typically Cover
Usually the underlying infrastructure availability (network, power, hypervisor) — NOT your specific application's uptime, which depends on your own software, configuration, and operational practices layered on top of that infrastructure.
What SLA Remedies Actually Provide
Typically service credits (a percentage of your hosting cost refunded or credited) proportional to the SLA breach — rarely compensation for actual business impact/lost revenue from downtime; read the specific terms rather than assuming broad compensation.
The Difference Between SLA and Actual Reliability
An SLA is a contractual commitment with a remedy if breached — it doesn't prevent downtime from happening, nor does the remedy typically make you financially whole for business impact; think of it as a baseline accountability mechanism, not a reliability guarantee in itself.
Your Own Application's Uptime Is a Separate Concern
Even with a provider offering a strong infrastructure SLA, your application can still experience downtime from your own code bugs, configuration errors, or insufficient capacity — see How to Define and Track SLOs and Error Budgets for tracking your actual, complete application uptime, which the provider's SLA alone doesn't guarantee.
Reading SLA Terms Carefully
Check specifically: what counts as "downtime" (does scheduled maintenance count?), how downtime is measured/verified, the claim process and deadline for requesting credits, and any exclusions (force majeure, actions outside the provider's control).
How Much Should SLA Percentage Influence Your Provider Choice?
A meaningful factor, but not the only one — also weigh actual historical reliability (harder to verify but often more informative than the contractual number), support quality, and overall fit for your specific technical needs.
Building Your Own Reliability Beyond the Provider's SLA
See How to Create a Disaster Recovery Plan for Your VPS and general redundancy/backup practices — your own operational practices ultimately determine your actual application reliability more than the provider's SLA percentage alone.
FAQ
Does a 99.99% SLA mean I'll never experience downtime?
No — it means the provider commits to that target and offers a remedy if they miss it; genuine, if infrequent, downtime can still occur even from providers with strong SLA commitments.
Continue Reading
- How to Define and Track SLOs and Error Budgets
- How to Create a Disaster Recovery Plan for Your VPS
- How to Evaluate a VPS Provider Before Committing (Checklist)
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