2 servers is the same as 1 server wrt fault tolerance, so yes, you are correct. If they want fault tolerance, they have to run 3 (or more).
On Fri, Jun 3, 2016 at 4:25 PM, Shawn Heisey <[email protected]> wrote: > On 6/3/2016 1:44 PM, Nomar Morado wrote: > > Is there any settings to override the quorum rule? Would you know the > > rationale behind it? Ideally, you will want to operate the application > > even if at least one data center is up. > > I do not know if the quorum rule can be overridden, or whether your > application can tell the difference between a loss of quorum and > zookeeper going down entirely. I really don't know anything about > zookeeper client code or zookeeper internals. > > From what I understand, majority quorum is the only way to be > *completely* sure that cluster software like SolrCloud or your > application can handle write operations with confidence that they are > applied correctly. If you lose quorum, which will happen if only one DC > is operational, then your application should go read-only. This is what > SolrCloud does. > > I am a committer on the Apache Solr project, and Solr uses zookeeper > when it is running in SolrCloud mode. The cloud code is handled by > other people -- I don't know much about it. > > I joined this list because I wanted to have the ZK devs include a > clarification in zookeeper documentation -- oddly enough, related to the > very thing we are discussing. I wanted to be sure that the > documentation explicitly mentioned that three serversare required for a > fault-tolerant setup. Some SolrCloud users don't want to accept this as > a fact, and believe that two servers should be enough. > > Thanks, > Shawn > >
