DataNodes can store blocks in multiple directories, usually located on different local drives. To set up multiple directories, you must specify a comma-separated list of pathnames as values under the dfs.data.dir/dfs.datanode.data.dir configuration parameters. DataNodes will try to put the same amount of data in each of the directories. NameNode also supports multiple directories where the namespace image and processing logs are stored. To set up multiple directories, one must specify a comma-separated list of pathnames as values under the configuration parameters dfs.name.dir/dfs.namenode.data.dir. The namespace directories are used for namespace data replication so that image and log can be recovered from the remaining disks/volumes if one of the disks fails.