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May 2017 Disk Performance

  • lowering dirty_background_{bytes,ratio} removes oscillations when more "memory work" is done
    • memory bandwidth is important
  • Writing ROOT files means an extra copy and currently no directIO
  • Using buffer cache could save a device read

3x root uninit
3x root uninit w/cpy

Command used:

$MRB_TOP/test.sh md125 true -ac1 -s dd ddb test_10Mx30000_bin{direct,buf}3 test_10Mx30000_root{4,3,2}

Which calls:
periodic_cmd_stats