All 7 Redis Sentinel & High Availability questions
More in Redis Sentinel & High Availability
What is Redis Sentinel, and what role does it play in providing high availability for a non clustered Redis setup? How does an application discover the current primary Redis instance when using Sentinel, especially after a failover has occurred? What is the quorum setting in a Sentinel configuration, and how does it affect the decision to trigger a failover? How do you check the current status of a Sentinel deployment to confirm it is properly monitoring your Redis primary and replicas? How would you deploy Redis Sentinel across multiple data centers or availability zones to maximize resilience against a localized failure? What is the difference between using Redis Sentinel and using Redis Cluster for achieving high availability, and how would you decide between them?
Advertisement
Back to results for “Redis Sentinel & High Availability”
Redis › Redis Sentinel & High Availability

Why does Redis Sentinel recommend running at least three Sentinel instances rather than just one?

Beginner

Answer

Running multiple Sentinel instances allows them to reach a quorum, meaning a majority agreement, before deciding a primary has actually failed and triggering a failover, which prevents a single Sentinel instance's own network issue or crash from incorrectly triggering an unnecessary failover based on a false alarm.
-- Three or more Sentinels provide reliable quorum based decisions
sentinel monitor mymaster 192.168.1.10 6379 2
Real-world example A team running three Sentinel instances across different servers avoids an unnecessary failover when just one Sentinel briefly lost network connectivity, since the remaining two correctly determined the primary was actually still healthy.

Common follow-ups: What is the quorum value in a Sentinel configuration, and how do you choose an appropriate one?;What happens if fewer Sentinels than the quorum value are currently reachable?

Redis Replication;Redis Architecture & Installation
All 7 Redis Sentinel & High Availability questions