• Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.17.0
    • Component/s: None
    • Labels:
    • Release Note:
      Change DFS block placement to allocate the first replica locally, the second off-rack, and the third intra-rack from the second.


      Currently, when writing out a block, dfs will place one copy to a local data node, one copy to a rack local node
      and another one to a remote node. This leads to a number of undesired properties:

      1. The block will be rack-local to two tacks instead of three, reducing the advantage of rack locality based scheduling by 1/3.

      2. The Blocks of a file (especiallya large file) are unevenly distributed over the nodes: One third will be on the local node, and two thirds on the nodes on the same rack. This may make some nodes full much faster than others,
      increasing the need of rebalancing. Furthermore, this also make some nodes become "hot spots" if those big
      files are popular and accessed by many applications.


        1. HADOOP-2559-1.patch
          8 kB
          Lohit Vijayarenu
        2. HADOOP-2559-2.patch
          11 kB
          Lohit Vijayarenu
        3. Trunk_Block_Report.png
          30 kB
          Lohit Vijayarenu
        4. Patch1_Block_Report.png.jpg
          52 kB
          Lohit Vijayarenu
        5. Patch2 Block Report.jpg
          56 kB
          Lohit Vijayarenu
        6. Trunk_Rack_Node_Mapping.jpg
          33 kB
          Lohit Vijayarenu
        7. Patch1_Rack_Node_Mapping.jpg
          34 kB
          Lohit Vijayarenu
        8. Patch2_Rack_Node_Mapping.jpg
          35 kB
          Lohit Vijayarenu
        9. HADOOP-2559-1.patch
          8 kB
          Lohit Vijayarenu
        10. HADOOP-2559-1-2.patch
          7 kB
          Lohit Vijayarenu
        11. HADOOP-2559-1-3.patch
          7 kB
          Lohit Vijayarenu
        12. HADOOP-2559-1-4.patch
          7 kB
          Lohit Vijayarenu

          Issue Links



              • Assignee:
                lohit Lohit Vijayarenu
                runping Runping Qi
              • Votes:
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                • Created: