Dear Wiki user, You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification. The "TroubleShooting" page has been changed by EliCollins: * The NameNode may be overloaded. Check the logs for messages that say "discarding calls..." * There may not be enough (any) DataNode nodes running for the data to be written. Again, check the logs. * Every DataNode on which the blocks were stored might be down (or not connected to the NameNode; it is impossible to distinguish the two). + * You may also get this message if permissions prevent the JT from creating on startup. + * If no datanode thinks it has any free space. Note that your datanode takes the freespace there is and subtracts "dfs.datanode.du.reserved" so even if there is free space, some times the datanode believes there isn't. You can visit the namenode status to check out how much space there is per datanode. === Error message: Could not obtain block ===