Suggest an editImprove this articleRefine the answer for “How does Sentinel differ from Redis Cluster?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)Redis Sentinel provides high availability for a single logical Redis instance through monitoring and automatic failover, but doesn't split data across nodes; Redis Cluster provides both scaling and high availability, distributing data across several master nodes via hash slots (16384 total). **Key point:** Sentinel is a simple HA scheme for one logical Redis with no scaling of data volume; Cluster is for large volumes of data spread across several servers, with limited support for multi-key operations (only within a single slot).Shown above the full answer for quick recall.Answer (EN)Image**Redis Sentinel** and **Redis Cluster** solve different problems: ### Redis Sentinel, a monitoring and automatic-failover system **Main goal:** to provide *high availability* for a single logical Redis instance. **How it works:** - Sentinel watches the master and its replicas. - If the master stops responding, the Sentinels hold a vote and **promote a replica to master**. - Clients find out about it and automatically switch to the new master. **What it gives you:** - Automatic failover (switching over on failure). - Monitoring the nodes' state. - Reassigning master/replica roles. **What it doesn't have:** - Sentinel **doesn't split data** across nodes (every copy holds *identical* data). - There's no scaling by data volume. It's used when you need: > A single logical Redis, with several copies for reliability. ### Redis Cluster, distributed data storage **Main goal:** to provide both *scaling* and *high availability* by **splitting data** across nodes. **How it works:** - Keys are distributed across several master nodes via hash slots (16384 in total). - Every master has one or several replicas. - If a master fails, its replica automatically becomes the new master. **What it gives you:** - Horizontal scaling (much more data can be stored). - High availability with no Sentinel needed. - Automatic recovery and request routing. **What it doesn't have:** - No full isolation, some data can become unavailable if a master and its replicas fail at the same time. - Some commands (multi-key) work in a limited way. It's used when you need: > A large volume of data, spread across several servers. ### A quick comparison: | Criterion | Redis Sentinel | Redis Cluster | |---|---|---| | Main goal | Fault tolerance | Scaling + fault tolerance | | Replication | Yes (1 master + N replicas) | Yes (several master-replica sets) | | Data distribution | No | Yes (by slots) | | Automatic failover | Yes | Yes | | Scaling | No | Yes | | Multi-key support | Full | Limited (within a single slot) | | Use | A simple HA scheme | A cluster for large data | **Summary:** - **Sentinel** makes Redis fault-tolerant, but not scalable. - **Cluster** makes Redis both fault-tolerant and scalable, by distributing data.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.