kubernetes
Redis Kubernetes Memory Calculator
Calculate how much memory your Redis deployment needs on Kubernetes. Accounts for dataset size, replication, overhead, and Redis Cluster mode.
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Sizing Redis on Kubernetes
Redis is an in-memory data store — all data lives in RAM. Correct memory sizing is critical: too little triggers OOM kills; too much wastes compute cost.
Memory Formula
per_replica_memory = dataset_size × (1 + overhead_pct)
total_memory = per_replica_memory × replicas × cluster_factorWhere cluster_factor = 1.1 for Redis Cluster, 1.0 for standalone.
Key Redis Memory Patterns
| Use Case | Overhead | Eviction Policy |
|---|---|---|
| Cache (ephemeral) | 20–30% | allkeys-lru |
| Session store | 30–50% | noeviction |
| Pub/Sub broker | 20% | noeviction |
| Sorted sets / leaderboards | 50–100% | volatile-lru |
Kubernetes Pod Configuration
resources:
requests:
memory: "8Gi" # from calculator
limits:
memory: "10Gi" # 1.2× request
env:
- name: REDIS_ARGS
value: "--maxmemory 8192mb --maxmemory-policy allkeys-lru"Redis Sentinel vs Redis Cluster
| Sentinel | Cluster | |
|---|---|---|
| Sharding | No — single dataset | Yes — hash slots |
| Failover | Automatic | Automatic |
| Max dataset | Single node RAM | N × node RAM |
| Complexity | Low | High |
| K8s operator | redis-operator | redis-operator (cluster mode) |
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
Why does Redis use more memory than my raw data size?
Redis stores each value with metadata — key expiry, type information, encoding, and a pointer. A string 'hello' (5 bytes) might occupy 60–80 bytes in Redis memory. For datasets with many small keys, overhead can be 30–100% of raw data size. Use OBJECT ENCODING <key> to inspect how Redis is storing individual values.
How do I set maxmemory in a Kubernetes Pod?
Set maxmemory in redis.conf or pass it as a flag: redis-server --maxmemory 8gb --maxmemory-policy allkeys-lru. Always set maxmemory to ~80% of your container memory limit — this leaves headroom for the Redis process itself and prevents OOM kills. The calculator's maxmemory output already accounts for this.
Do Redis replicas double my memory usage?
Yes — each replica holds a full copy of the dataset. 3 replicas (1 primary + 2 replicas) triple your memory usage. The tradeoff is high availability: replicas allow failover without data loss if the primary crashes. For pure caching where data loss is acceptable, replicas are optional.
What is Redis Cluster mode and when do I need it?
Redis Cluster shards data across multiple primary nodes using hash slots. It's needed when your dataset is too large for a single node, or when you need horizontal write scalability. For most use cases under ~50GB, a single primary with replicas (Sentinel) is simpler and sufficient. Redis Cluster adds operational complexity and does not support all Redis commands.
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