Kubernetes Resource Planning Guide
Kubernetes has become the industry standard for container orchestration, powering applications at scale for organizations worldwide. Proper resource planning is essential for running efficient, cost-effective Kubernetes clusters. This comprehensive guide will help you understand how to calculate and allocate resources for your Kubernetes deployments.
Understanding Kubernetes Resources
In Kubernetes, resources primarily refer to CPU and memory allocations for containers. Every container in a pod can specify resource requests and limits, which directly impact scheduling decisions and runtime behavior.
CPU Resources
CPU resources in Kubernetes are measured in "millicores" or "millicpu." One CPU core equals 1000 millicores. For example, if a container requests 250m (250 millicores), it's requesting 25% of one CPU core. CPU is a compressible resource, meaning containers can be throttled if they exceed their limits without being terminated.
Memory Resources
Memory is measured in bytes, but commonly expressed in mebibytes (Mi) or gibibytes (Gi). Unlike CPU, memory is incompressible - if a container exceeds its memory limit, it will be terminated (OOMKilled) and potentially restarted based on the pod's restart policy.
Resource Requests vs Limits
Understanding the difference between requests and limits is crucial for effective resource management:
Resource Requests
Requests define the minimum amount of resources a container needs to run. The Kubernetes scheduler uses requests to determine which node has sufficient resources to place the pod. A pod won't be scheduled unless a node can satisfy all container requests.
Resource Limits
Limits define the maximum resources a container can use. For CPU, exceeding the limit results in throttling. For memory, exceeding the limit results in the container being killed. Setting appropriate limits prevents runaway containers from affecting other workloads.
Best Practice Ratios
Industry best practices suggest the following ratios:
- CPU Limit/Request Ratio: 1.5x to 3x - allows for burst capacity while preventing excessive overcommitment
- Memory Limit/Request Ratio: 1.0x to 1.5x - memory should be more tightly controlled as it's incompressible
Calculating Cluster Resources
To calculate total cluster resources needed, consider these factors:
1. Workload Requirements
Start by calculating the total resources your workloads need:
- Total CPU = (Number of Pods) x (CPU per Pod) x (Replicas)
- Total Memory = (Number of Pods) x (Memory per Pod) x (Replicas)
2. System Overhead
Kubernetes system components (kubelet, kube-proxy, container runtime) require resources too. Plan for 15-25% overhead on each node for:
- kubelet and container runtime
- Operating system processes
- kube-proxy
- CNI (Container Network Interface) plugins
- Monitoring agents (Prometheus, Datadog, etc.)
3. Node Sizing
Choose node sizes based on your workload patterns:
- Small nodes (2-4 vCPU, 4-8GB RAM): Good for development, testing, or many small microservices
- Medium nodes (4-8 vCPU, 16-32GB RAM): Balanced option for most production workloads
- Large nodes (16+ vCPU, 64GB+ RAM): Best for memory-intensive applications or fewer, larger pods
Cloud Provider Considerations
Different cloud providers offer varying instance types and pricing:
AWS (Amazon EKS)
| Instance Type | vCPU | Memory | Price/Hour |
|---|---|---|---|
| t3.medium | 2 | 4 GB | ~$0.0416 |
| m5.large | 2 | 8 GB | ~$0.096 |
| m5.xlarge | 4 | 16 GB | ~$0.192 |
| m5.2xlarge | 8 | 32 GB | ~$0.384 |
Google Cloud (GKE)
| Instance Type | vCPU | Memory | Price/Hour |
|---|---|---|---|
| e2-medium | 2 | 4 GB | ~$0.0335 |
| e2-standard-2 | 2 | 8 GB | ~$0.067 |
| e2-standard-4 | 4 | 16 GB | ~$0.134 |
| e2-standard-8 | 8 | 32 GB | ~$0.268 |
Azure (AKS)
| Instance Type | vCPU | Memory | Price/Hour |
|---|---|---|---|
| Standard_B2s | 2 | 4 GB | ~$0.0416 |
| Standard_D2s_v3 | 2 | 8 GB | ~$0.096 |
| Standard_D4s_v3 | 4 | 16 GB | ~$0.192 |
| Standard_D8s_v3 | 8 | 32 GB | ~$0.384 |
Best Practices for Resource Allocation
1. Start with Requests, Not Limits
Begin by setting appropriate requests based on your application's baseline resource usage. Monitor actual usage over time before setting limits.
2. Use Vertical Pod Autoscaler (VPA)
VPA can automatically adjust resource requests based on historical usage, helping optimize resource allocation without manual intervention.
3. Implement Resource Quotas
Use ResourceQuotas to limit total resource consumption per namespace, preventing any single team or application from monopolizing cluster resources.
4. Set LimitRanges
LimitRanges define default requests and limits for pods in a namespace, ensuring all workloads have appropriate resource constraints.
5. Monitor and Iterate
Use tools like Prometheus and Grafana to monitor actual resource usage. Regularly review and adjust allocations based on real-world data.
6. Consider Pod Disruption Budgets
For high-availability workloads, set PodDisruptionBudgets to ensure a minimum number of replicas remain available during node maintenance or cluster operations.
Common Mistakes to Avoid
- Over-provisioning: Setting requests too high wastes cluster resources and increases costs
- Under-provisioning: Setting requests too low leads to resource contention and poor performance
- No limits: Without limits, a single container can consume all node resources
- Equal requests and limits: This prevents efficient resource sharing and burst capacity
- Ignoring system overhead: Forgetting to account for Kubernetes system components
Namespace Organization
Organize your cluster using namespaces for better resource management:
- kube-system: Kubernetes system components
- monitoring: Prometheus, Grafana, alerting
- ingress: Ingress controllers and load balancers
- production: Production workloads
- staging: Pre-production testing
- development: Development environments
Conclusion
Proper Kubernetes resource planning is essential for running efficient, cost-effective clusters. By understanding the relationship between requests and limits, accounting for system overhead, and following best practices, you can optimize your cluster for both performance and cost. Use our Kubernetes Resource Calculator above to estimate your cluster requirements and compare cloud provider costs.
Remember that resource planning is an iterative process. Start with reasonable estimates, monitor actual usage, and continuously refine your allocations based on real-world data.