kubernetes

Kubernetes Uptime SLA Calculator

Convert SLA percentages to real downtime. See exactly how many minutes of downtime 99.9%, 99.95%, and 99.99% actually allow per year, month, week, and day.

Understanding SLA Nines

SLA targets are expressed as a percentage of time the system is available. The "nines" shorthand refers to how many 9s appear in the percentage.

Downtime Budget Reference

SLA	Downtime/year	Downtime/month	Downtime/day
99.0%	3.65 days	7.3 hours	14.4 min
99.5%	1.83 days	3.6 hours	7.2 min
99.9%	8.76 hours	43.8 min	1.44 min
99.95%	4.38 hours	21.9 min	43.2 sec
99.99%	52.6 min	4.4 min	8.6 sec
99.999%	5.26 min	26.3 sec	0.86 sec

Kubernetes SLA Layers

Your overall SLA is the product of all layers:

Total SLA = control_plane_sla × worker_sla × network_sla × storage_sla

If each layer is 99.99%, your total is: 0.9999⁴ = 99.96% — still only three nines.

What Breaks 99.9%

›A single unplanned node reboot: ~5 min (if pods reschedule immediately)
›A botched rolling update: 10–30 min
›etcd quorum loss: hours (requires manual recovery)
›Network partition: depends on timeout + recovery

PodDisruptionBudget for Planned Maintenance

yaml

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: my-app-pdb
spec:
  minAvailable: 2   # keep at least 2 pods up during node drain
  selector:
    matchLabels:
      app: my-app

Key Terms

Full glossary →

kubeadm

A tool for bootstrapping Kubernetes clusters. It automates the setup of control plane components and joining worker nodes, following Kubernetes best practices.

etcd

A distributed key-value store used by Kubernetes to store all cluster state and configuration. etcd is the single source of truth for the entire cluster.

cert-manager

A Kubernetes controller for automating TLS certificate management. cert-manager can issue certificates from Let's Encrypt, Vault, or internal CAs, and automatically renews them.

Helm

A package manager for Kubernetes. Helm charts bundle Kubernetes manifests into reusable packages with configurable values, versioned and published to chart repositories.

Frequently Asked Questions

What does 99.9% uptime actually mean?

99.9% uptime allows 8.76 hours of downtime per year — that's about 43.8 minutes per month or 10 minutes per week. It sounds high but is actually a fairly modest target. Most Kubernetes clusters running on self-managed infrastructure realistically achieve 99.9–99.95%.

What SLA does a managed Kubernetes service guarantee?

Major cloud providers typically guarantee 99.9–99.95% for their control plane SLA. GKE, EKS, and AKS all offer ~99.95% for the API server. Note: worker node uptime is separate and depends on your instance types. Spot/preemptible nodes do not contribute to your SLA.

Can I achieve 99.99% on self-hosted Kubernetes?

Yes, but it requires significant investment: multi-region or multi-AZ control plane, redundant load balancers, automated failover, and rigorous change management. Most self-hosted setups targeting 99.99% use a dedicated HA etcd cluster, 3+ control plane nodes across AZs, and active-active load balancers (Keepalived + HAProxy).

How does planned maintenance affect my SLA budget?

Planned maintenance counts against your SLA unless you have zero-downtime rolling upgrades. For 99.9% (8.76 hrs/year), a single 30-minute maintenance window consumes 6% of your annual budget. Use rolling updates, PodDisruptionBudgets, and the Kubernetes upgrade path planner to minimise disruption.

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