Installing and running “redis” seem to be enough to run Drupal with it - but sometimes you want to scale Redis for HA. Tool named “redis-sentinel” provides “redis” services such as: Monitoring: It can check master or slave services whether is working correctly and healthy or not. Notification: It can notify when a service goes down. Automatic Failover: It starts a failover scenario and assigns one of slaves as a master when master service goes down.