On Thu, Dec 6, 2012 at 5:21 PM, Jack Krupansky <j...@basetechnology.com> wrote: > If 1 is the minimum, what is the 3 "minimum" all about?
The minimum for running an ensemble (a cluster) and having any sort of fault tolerance? > The zk web page does say "Three ZooKeeper servers is the minimum recommended > size for an ensemble, and we also recommend that they run on separate > machines" - but it does say "recommended". > > But back to the original question - it sounds as if 4 nodes would the > recommended minimum number of nodes if you want to tolerate one machine > going down and maintaining that 3 zookeeper recommended minimum ensemble. Nope - the "ensemble" are not the number of servers that are currently up, but the number in the cluster. This is important to prevent split brain. 3 ZK servers means that a majority of the servers is 2, hence you can lose 1. 5 ZK servers means that a majority of the servers is 3, hence you can lose 2. -Yonik http://lucidworks.com
