- The HDFS namespace is stored by the NameNode.
- The entire file system namespace, including the mapping of blocks to files and file system properties, is stored in a file called the FsImage.
- The FsImage is stored as a file in the NameNode’s local file system too.
- The NameNode keeps an image of the entire file system namespace and file Blockmap in memory.
- Reads at startup only and keeps it during the life of start
- RAM Dependency
- What about “One Large File” or “1,000,000 small files”
Step 1: First save the fsimage to local file system (Note: You cannot save the fsimage to HDFS.)
Step 2: Converting saved image to human readable file using –oiv option
Step 3: Now you can open the file in your favorite editor or you can try $head or $tail quickly to peek into.