On 8/20/2015 1:49 AM, Merlin Morgenstern wrote: > I am running 2 dedicated servers on which I plan to install Solrcloud with > 2 solr nodes and 3 ZK. > > From Stackoverflow I learned that the best method for autostarting > zookeeper on ubuntu 14.04 is to install it via "apt-get install > zookeeperd". I have that running now. > > How could I add a second zookeeper to one machine? The config only allows > one. Or if this is not possible, what would be the recommended way to get 3 > ZK on 2 dedicated running? > > I have followed a tutorial where I have that setup available va bash > script, but it seems that the ubuntu zookeeper setup is robust as it offers > zombie processes and a startup script as well.
It is possible to have multiple zookeeper installs on one machine, but if you do this, your system will not be fault tolerant. A simple fact of life is that hardware can fail, and it can fail completely. If the motherboard in a server develops a fault, the entire server is probably going to fail. If the machine with two zookeepers on it dies, zookeeper quorum will be lost and SolrCloud will go read-only. It will not be possible to write to it, even though there is still a surviving machine. Redundant zookeeper requires three completely separate machines, so that if you lose any one of those machines, the cluster still has a majority present and stays completely operational. This means that SolrCloud requires three machines minimum. The third server can be a much less capable machine that runs zookeeper only, but it must be there in order to achieve true fault tolerance. Thanks, Shawn
