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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. |
DatanodeInfo | DatanodeInfo tracks stats on a given DataNode, such as available storage capacity, last update time, etc. |
DataNodeReport | A report on the status of a DataNode. |
DFSck | This class provides rudimentary checking of DFS volumes for errors and sub-optimal conditions. |
DFSck.Result | Result of checking, plus overall DFS statistics. |
DFSShell | This class provides some DFS administrative access. |
DistributedFileSystem | Implementation of the abstract FileSystem for the DFS system. |
NameNode | NameNode serves as both directory namespace manager and "inode table" for the Hadoop DFS. |
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. |
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.
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