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mapreduce - CS 345A Data Mining MapReduce Singlenode...

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    CS 345A Data Mining MapReduce
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Single-node architecture Memory Disk CPU Machine Learning, Statistics “Classical” Data Mining
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Commodity Clusters Web data sets can be very large  Tens to hundreds of terabytes Cannot mine on a single server (why?) Standard architecture emerging: Cluster of commodity Linux nodes Gigabit ethernet interconnect How to organize computations on this  architecture? Mask issues such as hardware failure
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Cluster Architecture Mem Disk CPU Mem Disk CPU Switch Each rack contains 16-64 nodes Mem Disk CPU Mem Disk CPU Switch Switch 1 Gbps between  any pair of nodes in a rack 2-10 Gbps backbone between racks
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Stable storage First order problem: if nodes can fail, how  can we store data persistently?  Answer: Distributed File System Provides global file namespace Google GFS; Hadoop HDFS; Kosmix KFS Typical usage pattern Huge files (100s of GB to TB) Data is rarely updated in place Reads and appends are common
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Distributed File System Chunk Servers File is split into contiguous chunks Typically each chunk is 16-64MB Each chunk replicated (usually 2x or 3x) Try to keep replicas in different racks Master node a.k.a. Name Nodes in HDFS Stores metadata Might be replicated Client library for file access Talks to master to find chunk servers  Connects directly to chunkservers to access data
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Warm up: Word Count We have a large file of words, one word to  a line
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