Package org.apache.hadoop.dfs

A distributed implementation of FileSystem.

See:
Description

Interface Summary

FSConstants

Some handy constants

Class Summary

DataNode	DataNode is a class (and program) that stores a set of blocks for a DFS deployment.
DatanodeDescriptor	DatanodeDescriptor tracks stats on a given DataNode, such as available storage capacity, last update time, etc., and maintains a set of blocks stored on the datanode.
DatanodeID	DatanodeID is composed of the data node name (hostname:portNumber) and the data storage ID, which it currently represents.
DatanodeInfo	DatanodeInfo represents the status of a DataNode.
DFSAdmin	This class provides some DFS administrative access.
DFSck	This class provides rudimentary checking of DFS volumes for errors and sub-optimal conditions.
DistributedFileSystem	Implementation of the abstract FileSystem for the DFS system.
FsckServlet	This class is used in Namesystem's jetty to do fsck on namenode.
GetImageServlet	This class is used in Namesystem's jetty to retrieve a file.
JspHelper
NameNode	NameNode serves as both directory namespace manager and "inode table" for the Hadoop DFS.
NamenodeFsck	This class provides rudimentary checking of DFS volumes for errors and sub-optimal conditions.
SecondaryNameNode	The Secondary NameNode is a helper to the primary NameNode.
SecondaryNameNode.GetImageServlet	This class is used in Namesystem's jetty to retrieve a file.
StreamFile

Enum Summary

DatanodeInfo.AdminStates
FSConstants.NodeType	Type of the node
FSConstants.SafeModeAction
FSConstants.StartupOption

Exception Summary

AlreadyBeingCreatedException	The exception that happens when you ask to create a file that already is being created, but is not closed yet.
LeaseExpiredException	The lease that was being used to create this file has expired.
NotReplicatedYetException	The file has not finished being written to enough datanodes yet.
SafeModeException	This exception is thrown when the name node is in safe mode.

Package org.apache.hadoop.dfs Description

A distributed implementation of FileSystem. This is loosely modelled after Google's GFS.

The most important difference is that unlike GFS, Hadoop DFS files have strictly one writer at any one time. Bytes are always appended to the end of the writer's stream. There is no notion of "record appends" or "mutations" that are then checked or reordered. Writers simply emit a byte stream. That byte stream is guaranteed to be stored in the order written.