[LU-8786] Terrible i/o performance of a test application doing repeatable writes and truncates

Duplicate — Tue, 4 Dec 2018 13:37:08 +0000

A customer application benchmark required for acceptance testing shows terrible i/o performance. A simple test case was created to mimic the customer application behavior. This test never completes when run with a walltime limit of 30 minutes (job is killed after walltime exceeded); the same test run to the /tmp fs on the client node completes within a few seconds.
The tests completes in few seconds in Lustre-2.1.

 program iotest
      PARAMETER (NA=6400)
      dimension IA(NA)
      call init (IA,NA)
      call sleep(1)
      open (unit=22, file='time.step')
      do i=1,na
      call my_write(iA,NA,i)
      end do
      STOP
      END
      SUBROUTINE my_write(IA,NA,I)
      dimension ia(na)
      kt=ia(i)
      WRITE ( 22, '(1x, i8)' )   kt
      REWIND (22)
      return
      end
      subroutine init(IA,NA)
      dimension iA(na)
      do i=1,NA
      ia(i)=i
      end do
      return
      end

Whamcloud Community JIRA

[LU-8786] Terrible i/o performance of a test application doing repeatable writes and truncates