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LOCAL In local mode, you may use any Lucene Directory implementation. And it doesn't matter what you set indexLocalOnly to.  REPLICATION In replication mode, indexes can either be stored locally on each node (RAMDirectory, FSDirectory, etc) but you need to set indexLocalOnly to false. Any Directory implementation should work. Alternately, if you use some form of shared storage for indexes (see Sharing the Index), you can then set indexLocalOnly to true.  DISTRIBUTION and INVALIDATION For these 2 cache modes, you need to use a shared index and set indexLocalOnly to true. In future, we will be able to deal with truly distributed queries, but that would be after ISPN-200.