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  1. Cassandra
  2. CASSANDRA-7386

JBOD threshold to prevent unbalanced disk utilization

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    • Type: Improvement
    • Status: Resolved
    • Priority: Low
    • Resolution: Fixed
    • Fix Version/s: 2.0.12, 2.1.3
    • Component/s: None
    • Labels:


      Currently the pick the disks are picked first by number of current tasks, then by free space. This helps with performance but can lead to large differences in utilization in some (unlikely but possible) scenarios. Ive seen 55% to 10% and heard reports of 90% to 10% on IRC. With both LCS and STCS (although my suspicion is that STCS makes it worse since harder to be balanced).

      I purpose the algorithm change a little to have some maximum range of utilization where it will pick by free space over load (acknowledging it can be slower). So if a disk A is 30% full and disk B is 5% full it will never pick A over B until it balances out.


        1. patch_2_1_branch_proto.diff
          10 kB
          Chris Lohfink
        2. 7386-v1.patch
          15 kB
          Robert Stupp
        3. Mappe1.ods
          62 kB
          Robert Stupp
        4. 7386v2.diff
          23 kB
          Robert Stupp
        5. mean-writevalue-7disks.png
          48 kB
          Lyuben Todorov
        6. sstable-count-second-run.png
          30 kB
          Lyuben Todorov
        7. 7386-2.0-v3.txt
          16 kB
          Robert Stupp
        8. 7386-2.1-v3.txt
          18 kB
          Robert Stupp
        9. test1_no_patch.jpg
          53 kB
          Alan Boudreault
        10. test1_with_patch.jpg
          59 kB
          Alan Boudreault
        11. test2_no_patch.jpg
          65 kB
          Alan Boudreault
        12. test2_with_patch.jpg
          69 kB
          Alan Boudreault
        13. test3_no_patch.jpg
          59 kB
          Alan Boudreault
        14. test3_with_patch.jpg
          73 kB
          Alan Boudreault
        15. 7386-2.0-v4.txt
          23 kB
          Robert Stupp
        16. 7386-2.1-v4.txt
          26 kB
          Robert Stupp
        17. 7386-2.0-v5.txt
          148 kB
          Robert Stupp
        18. 7386-2.1-v5.txt
          26 kB
          Robert Stupp
        19. test_regression_no_patch.jpg
          84 kB
          Alan Boudreault
        20. test_regression_with_patch.jpg
          94 kB
          Alan Boudreault

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            • Assignee:
              snazy Robert Stupp Assign to me
              cnlwsu Chris Lohfink
              Robert Stupp
              Yuki Morishita
              Alan Boudreault


              • Created:

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