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

        Issue Links



            • Assignee:
              Lohit Vijayarenu
              Runping Qi
            • Votes:
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              2 Start watching this issue


              • Created: