Suggest an editImprove this articleRefine the answer for “How many Sentinel instances are recommended at minimum?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)The minimum recommended is three Sentinel instances: Sentinel makes decisions (e.g. about a failover) only by majority vote, and with three, a majority (2 of 3) can always be reached, whereas with two, agreement could end up 1:1 and the system would "hang". **Key point:** the optimal number is odd (3, 5, 7), so a majority can always be reached during a vote; three Sentinels also guard against false positives, if one node gets it wrong, the others can overrule it.Shown above the full answer for quick recall.Answer (EN)ImageThe minimum recommended is **three Sentinel instances**. ### Why exactly three: 1. **Quorum and voting.** Sentinel makes decisions (e.g. about a failover) **only by majority vote**. - With two instances, agreement could end up 1:1, and the system would "hang". - With three, a majority (2 of 3) can always be reached. 2. **Fault tolerance.** If one Sentinel goes down, the other two can keep monitoring and carry out a failover. With two instances, one failing already makes the system non-functional. 3. **Detection accuracy.** Three Sentinels help avoid false positives (if one node gets it wrong, the rest can overrule it). ### Summary: > Minimum: **3 Sentinel processes**, > Optimal: **an odd number (3, 5, 7)**, so a majority vote can always be reached.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.