Where and how Solr stores its indexes are configurable options.

Specifying a Location for Index Data with the dataDir Parameter

By default, Solr stores its index data in a directory called `/data` under the core’s instance directory (`instanceDir`). If you would like to specify a different directory for storing index data, you can configure the `dataDir` in the `core.properties` file for the core, or use the `<dataDir>` parameter in the `solrconfig.xml` file. You can specify another directory either with an absolute path or a pathname relative to the instanceDir of the SolrCore. For example:

``<dataDir>/solr/data/${solr.core.name}</dataDir>`` The `${solr.core.name}` substitution will cause the name of the current core to be substituted, which results in each core’s data being kept in a separate subdirectory.

If you are using replication to replicate the Solr index (as described in Legacy Scaling and Distribution), then the `<dataDir>` directory should correspond to the index directory used in the replication configuration.

 If the environment variable `SOLR_DATA_HOME` is defined, or if `solr.data.home` is configured for your DirectoryFactory, or if `solr.xml` contains an element `` then the location of data directory will be `//data`.

Specifying the DirectoryFactory For Your Index

The default `solr.NRTCachingDirectoryFactory` is filesystem based, and tries to pick the best implementation for the current JVM and platform. You can force a particular implementation and/or configuration options by specifying `solr.MMapDirectoryFactory`, `solr.NIOFSDirectoryFactory`, or `solr.SimpleFSDirectoryFactory`.

``````<directoryFactory name="DirectoryFactory"
class="solr.MMapDirectoryFactory">
The `solr.RAMDirectoryFactory` is memory based, not persistent, and does not work with replication. Use this DirectoryFactory to store your index in RAM.
``<directoryFactory class="org.apache.solr.core.RAMDirectoryFactory"/>``
 If you are using Hadoop and would like to store your indexes in HDFS, you should use the `solr.HdfsDirectoryFactory` instead of either of the above implementations. For more details, see the section Running Solr on HDFS.