FSCK prints the full identifier of a block, which is useful in some contexts depending on what you're about to troubleshoot or investigate. Here's a break down: BP-929597290-192.0.0.2-1439573305237 = This is a BlockPool (BP) ID. Its the mark of a NameNode's ownership of the block in question. You might recall that HDFS now supports federated namespaces, wherein multiple NameNodes may be served by a single DataNode. This ID is how each NameNode is uniquely identified to be the owner of a held block ID. Even though you do not explicitly utilise federation, the block-pool concept is now inbuilt into the identifier design of HDFS by default. See http://archive.cloudera.com/cdh5/cdh/5/hadoop/hadoop-project-dist/hadoop-hdfs/Federation.html#Multiple_NamenodesNamespaces blk_1074084574_344316 = This is the block ID (blk_X_Y). Each block under every file is uniquely identified by a number X and a sub-number Y (generation stamp). More on block IDs and HDFS architecture can be read in the AOS book: http://aosabook.org/en/hdfs.html DS-730a75d3-046c-4254-990a-4eee9520424f,DISK = This is a storage identifier ID. It helps tell that on the specified DN IP:PORT, which disk (hashed identifier) is actually the one holding the data, and what is the type of the disk (DISK). HDFS now supports tiered storage, in which this comes useful: http://archive.cloudera.com/cdh5/cdh/5/hadoop/hadoop-project-dist/hadoop-hdfs/ArchivalStorage.html (aside of other things).
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