Hadoop HDFS: The Ultimate Storage
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Transcript of Hadoop HDFS: The Ultimate Storage
Nodes
• NameNode (metadata)
• 1
• or 2 (NamenodeHA + 3 JournalNodes)
• DataNode (blocks)
• 3~ nodes
• Rack awareness
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Filesystem
• Metadata on Namenode JVM heap
• "OK, Namenode should have giant RAM"
• File with Blocks (default 64MB)
• Block level compression & parallel read
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Compression
• Gzip, Bzip2, ....
• By filename suffix!
• By HDFS specific container file feature
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Protocol
• Java (DFSClient) Native Protocol
• Binary protocol
• Version sensitive
• All clients communicate with all nodes
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Protocol #2• WebHDFS (Hadoop v1.0~)
• HTTP
• Protocol version defined
• All clients communicate with all nodes
• HttpFs (Hadoop v2.0~)
• HTTP proxy server for DFSClient
• All clients communicate with a node
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Performance
• HDFS is for sequencial access
• and for large (128MB or more) files
• HDFS is not for random access
• HBase is perfect software for you!
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