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What is the meaning of the namespace and metadata used in hdfs (namenode)

As a newbie to hadoop, I get confused with these words namespaces and metadata. Is there a connection between the two?

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According to "Hadoop" Ultimate Guide "-" NameNode manages the file system namespace. It supports the file system tree and metadata for all files and directories in the tree. "

Essentially, a namespace means a container. In this context, this means a grouping of file names or a hierarchy structure.

Metadata contains things like file owners, permission bits, block locations, size, etc.

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A namespace is nothing more than a term that we use to describe the tree structure of the file system.

Basically, when we say a namespace, we mean a certain place in hdfs.

'/ or' root dir is the namespace. The folder / user is a namespace. In Hadoop, we call the namespace the directory that the name node handles.

link: https://www.quora.com/What-is-%E2%80%98Namespace%E2%80%99-in-HDFS-and-what-would-be-the-contents-residing-in-a -% E2% 80% 98Namespace% E2% 80% 99

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to make it simpler / clearer, and since HDFS is another file system, we can give an example of the Windows file system:
Suppose you have a file: test.txt in this path C: \ User \ Test \ New Folder \ Test.txt.
therefore, in the case of windows, this path is a namespace .
Now, if you go to the properties of this file, you will find some information (date of creation, last modification, owner ...), this information is metadata, it is called so because it represents a higher level of abstraction (data file contents and metadata - this is the description of the file itself).
In the same way, we can use the same example for HDFS, so the namespace is the path to the data block, and the metadata is information about the block that he himself

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Source: https://habr.com/ru/post/970011/

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