[antirez]

Hello, Sentinel 2 is doing quite a good work for many users, here is for example Flickr report: http://code.flickr.net/2014/07/31/redis-sentinel-at-flickr/

Of course Sentinel does not make Redis conceptually different from what it is from the point of view of consistency guarantees during failures. It performs best-effort attempt to select the best slave to retain writes, but under certain failure modes its possible to lose writes during a failover.

This is common with many failover solutions of *SQL systems as well btw. It depends on your use case if this is an affordable risk or not. For most Redis use cases, usually the risk of losing some writes after certain failovers is not a big issue. For other use cases it is, and a store that retains the writes during all the failure scenarios should be used.