On Tue, 17 Jul 2012, Michael Hase wrote:

To work around these caching effects just use a file > 2 times the size of ram, iostat then shows the numbers really coming from disk. I always test like this. a re-read rate of 8.2 GB/s is really just memory bandwidth, but quite impressive ;-)


Ok, the iozone benchmark finally completed. The results do suggest that reading from mirrors substantially improves the throughput. This is interesting since the results differ (better than) from my 'virgin mount' test approach:

Command line used: iozone -a -i 0 -i 1 -y 64 -q 512 -n 8G -g 256G

              KB  reclen   write rewrite    read    reread
         8388608      64  572933 1008668  6945355  7509762
         8388608     128 2753805 2388803  6482464  7041942
         8388608     256 2508358 2331419  2969764  3045430
         8388608     512 2407497 2131829  3021579  3086763
        16777216      64  671365  879080  6323844  6608806
        16777216     128 1279401 2286287  6409733  6739226
        16777216     256 2382223 2211097  2957624  3021704
        16777216     512 2237742 2179611  3048039  3085978
        33554432      64  933712  699966  6418428  6604694
        33554432     128  459896  431640  6443848  6546043
        33554432     256  444490  430989  2997615  3026246
        33554432     512  427158  430891  3042620  3100287
        67108864      64  426720  427167  6628750  6738623
        67108864     128  419328  422581  6666153  6743711
        67108864     256  419441  419129  3044352  3056615
        67108864     512  431053  417203  3090652  3112296
       134217728      64  417668   55434   759351   760994
       134217728     128  409383  400433   759161   765120
       134217728     256  408193  405868   763892   766184
       134217728     512  408114  403473   761683   766615
       268435456      64  418910   55239   768042   768498
       268435456     128  408990  399732   763279   766882
       268435456     256  413919  399386   760800   764468
       268435456     512  410246  403019   766627   768739

Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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