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  == ZooKeeper ==
  Multiple Zookeeper servers running together for fault tolerance and high 
availability is called an ensemble.  For production, it's recommended that you 
run an external zookeeper ensemble rather than having Solr run embedded 
servers.  See the [[http://zookeeper.apache.org/|Apache ZooKeeper]] site for 
more information on downloading and running a zookeeper ensemble. More 
specifically, try 
[[http://zookeeper.apache.org/doc/r3.3.4/zookeeperStarted.html|Getting 
Started]] and 
[[http://zookeeper.apache.org/doc/r3.3.4/zookeeperAdmin.html|ZooKeeper Admin]]. 
It's actually pretty simple to get going. You can stick to having Solr run 
ZooKeeper, but keep in mind that a ZooKeeper cluster is not easily changed 
dynamically. Until further support is added to ZooKeeper, changes are best done 
with rolling restarts. Handling this in a separate process from Solr will 
usually be preferable. 
  
+ When Solr runs an embedded zookeeper server, it defaults to using the solr 
port plus 1000 for the zookeeper client port.  In addition, it defaults to 
adding one to the client port for the zookeeper server port, and two for the 
zookeeper leader election port.  So in the first example with Solr running at 
8983, the embedded zookeeper server used port 9983 for the client port and 
9984,9985 for the server ports.
+ 
  In terms of trying to make sure ZooKeeper is setup to be very fast, keep a 
few things in mind: Solr does not use ZooKeeper intensively - optimizations may 
not be necessary in many cases. Also, while adding more ZooKeeper nodes will 
help some with read performance, it will slightly hurt write performance. 
Again, Solr does not really do much with ZooKeeper when your cluster is in a 
steady state. If you do need to optimize ZooKeeper, here are a few helpful 
notes:
  
   1. ZooKeeper works best when it has a dedicated machine. ZooKeeper is a 
timely service and a dedicated machine helps ensure timely responses. A 
dedicated machine is not required however.
   2. ZooKeeper works best when you put its transaction log and snap-shots on 
different disk drives.
   3. If you do colocate ZooKeeper with Solr, using separate disk drives for 
Solr and ZooKeeper will help with performance.
  
- When Solr runs an embedded zookeeper server, it defaults to using the solr 
port plus 1000 for the zookeeper client port.  In addition, it defaults to 
adding one to the client port for the zookeeper server port, and two for the 
zookeeper leader election port.  So in the first example with Solr running at 
8983, the embedded zookeeper server used port 9983 for the client port and 
9984,9985 for the server ports.
  
  == Managing collections via the Collections API ==
  

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