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  1. Kudu
  2. KUDU-1952

round-robin block allocation can place all blocks for a given column on one disk

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 1.3.0
    • Fix Version/s: 1.5.0
    • Component/s: fs, perf
    • Labels:
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      Description

      Currently the LBM allocates across disks in round-robin order. I ran a test using 4 data disks and a table with 12 columns. This caused very uneven allocation across disks, since all data for column N ended up on disk N%4. This also makes single-column scans slow since they read from only a single disk.

      In a more mixed workload this is likely to be less problematic, but still it seems like we should take available space into consideration for allocation, and/or add more randomness.

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              • Assignee:
                andrew.wong Andrew Wong
                Reporter:
                tlipcon Todd Lipcon
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                • Created:
                  Updated:
                  Resolved: