Size Elasticsearch shards, replicas and node count for an index.
Shard size drives query performance: too small and coordination overhead dominates, too large and recovery and rebalancing become slow. Replicas multiply storage but are what allow the cluster to lose a node without data loss. Over-sharding is the most common Elasticsearch mistake, because each shard carries fixed heap and file handle costs regardless of how little data it holds.
Elasticsearch Shard
Primary shards = total data ÷ target shard size; total = primaries × (1 + replicas)
Primary shards = total data ÷ target shard size; total = primaries × (1 + replicas) Shard size drives query performance: too small and coordination overhead dominates, too large and recovery and rebalancing become slow. Replicas multiply storage but are what allow the cluster to lose a node without data loss.
Over-sharding is the most common Elasticsearch mistake, because each shard carries fixed heap and file handle costs regardless of how little data it holds.
This calculator takes 5 inputs: Daily ingest volume, Retention period, Target shard size, Replicas per shard, Usable storage per node. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.