The article explores the file structure and data management within Elasticsearch's data directory, focusing on node, index, and shard levels. It details the various paths used by Elasticsearch, such as path.home, path.conf, and path.data, and explains the roles of both Elasticsearch and Lucene in handling data storage. The text examines node data files, like the global state file and node.lock, and index data, illustrating how index state files store metadata. It further delves into shard data management, including the transaction log's role in maintaining performance by delaying full Lucene commits, and the structure of Lucene index files. The article also discusses the use of the Lucene CheckIndex tool for resolving shard issues and outlines the snapshot storage process, which includes renaming files to avoid conflicts when indexes are recreated and resnapshotted. Additionally, an editor's note updates readers on a change in Elasticsearch version 6.0 regarding content type headers in curl commands.