2

I am not sure why this is happening but these are totally false results:

    Children see throughput for 15 re-readers       = 12793134.62 KB/sec
    Parent sees throughput for 15 re-readers        = 12753940.84 KB/sec
    Min throughput per process                      =  515695.50 KB/sec 
    Max throughput per process                      = 1088000.75 KB/sec
    Avg throughput per process                      =  852875.64 KB/sec
    Min xfer                                        =  249856.00 KB

    Children see throughput for 15 random readers   = 12667347.75 KB/sec
    Parent sees throughput for 15 random readers    = 12613558.90 KB/sec
    Min throughput per process                      =  685239.00 KB/sec 
    Max throughput per process                      = 1318021.25 KB/sec
    Avg throughput per process                      =  844489.85 KB/sec
    Min xfer                                        =  274432.00 KB

The command executed: iozone -i 0 -i 1 -i 2 -r 4m -s 512m -t 15

5

Your test size is 512 Mb. So you measure how your system respond to this load.
Your system have much more than 512 Mb of memory, so everything is read/writen to cache. So your results seems relevant.

If you want to test your disk, you have to use a much bigger dataset. Say twice the memory size. And flush the cache before each run: echo 3 > /proc/sys/vm/drop_caches

1

Couple of extras I added to my iozone test. Got better results.

  • umount the file system between each iteration , if your doing multiple.
  • add -c , -C , -e options.

    iozone -c -C -e -M -o -p -R -+r -i 0 -i 1 -i 2 -i 4 -i 5 -i 6 -i 7 -i 8

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