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From Apache Wiki <>
Subject [Solr Wiki] Trivial Update of "SolrCloud" by YonikSeeley
Date Wed, 03 Feb 2010 17:13:30 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Solr Wiki" for change notification.

The "SolrCloud" page has been changed by YonikSeeley.
The comment on this change is: add TOC.


   * Automatic load balancing and fail-over for queries
  Zookeeper is integrated and used to coordinate and store the configuration of the cluster.
+ <<TableOfContents(3)>>
  == Getting Started ==
  SolrCloud is currently under development!
@@ -104, +106 @@

  To demonstrate fail over for high availability, go ahead and kill any one of the Solr servers
(just press CTRL-C in the window running the server) and and send another query request to
any of the remaining servers that are up.
- === Two shard cluster with shard replicas and zookeeper ensemble ===
+ === Example C: Two shard cluster with shard replicas and zookeeper ensemble ===
  The problem with example B is that while there are enough Solr servers to survive any one
of them crashing, there is only one zookeeper server that contains the state of the cluster.
 If that zookeeper server crashes, distributed queries will still work since the solr servers
remember the state of the cluster last reported by zookeeper.  The problem is that no new
servers or clients will be able to discover the cluster state, and no changes to the cluster
state will be possible.
  Running multiple zookeeper servers in concert (a zookeeper ensemble) allows for high availability
of the zookeeper service.  Every zookeeper server needs to know about every other zookeeper
server in the ensemble, and a majority of servers are needed to provide service.  For example,
a zookeeper ensemble of 3 servers allows any one to fail with the remaining 2 constituting
a majority to continue providing service.  5 zookeeper servers are needed to allow for the
failure of up to 2 servers at a time.

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