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NFS-write blocks all processes [message #51707] Thu, 16 October 2014 10:56 Go to previous message
Bernd_K is currently offline  Bernd_K
Messages: 2
Registered: October 2014
Junior Member
Hi All.

Most likely a simple problem - but I'm obviously unable to solve it Smile

When my processes NFS-write to the RAID, all processes are "blocked" (don't do anything) until the write operation is completed.
The reason for "don't do anything" seems to be, that all NFS-read is stopped while the NFS-write is going on.

"iostat -nkx 1" looks like this:

Device:rkB_nor/s    wkB_nor/s rkB_dir/s wkB_dir/s    rkB_svr/s    wkB_svr/s 

pr2     10232.00     10234.50      0.00      0.00     16384.00     59935.75 
pr2     57235.25     57223.15      0.00      0.00     60416.00         0.00 
pr2     56915.50     56932.60      0.00      0.00     61440.00         0.00 
pr2     67707.06     67702.07      0.00      0.00     54272.00         0.00
pr2     54517.38     54557.34      0.00      0.00     59392.00         0.00 
pr2     54597.31     54557.34      0.00      0.00     62464.00         0.00 
pr2     65770.36     65775.69      0.00      0.00     53734.65         0.00 
pr2     54517.38     54514.49      0.00      0.00     61440.00         0.00 
pr2     60912.38     60909.88      0.00      0.00     56320.00         0.00 
pr2     54517.38     54557.34      0.00      0.00     61440.00         0.00 
pr2     54597.31     54557.34      0.00      0.00     61440.00         0.00 
pr2     36371.56     36371.56      0.00      0.00     26624.00         0.00 
pr2     54517.38     54557.34      0.00      0.00     52224.00         0.00 
pr2     54597.31     54557.34      0.00      0.00     53248.00         0.00 
pr2     55716.44     55693.96      0.00      0.00     58368.00         0.00 
pr2     59473.50     59533.45      0.00      0.00     60416.00         0.00 
pr2     49149.69     49090.33      0.00      0.00     59817.82         0.00 
pr2     54517.38     54557.34      0.00      0.00     38912.00         0.00 
pr2     20304.12     20279.54      0.00      0.00     23552.00     71680.00 
pr2       639.50       694.07      0.00      0.00         0.00    105611.52 
pr2         0.00         0.00      0.00      0.00         0.00    114688.00 
pr2         0.00         0.00      0.00      0.00         0.00    115712.00 
pr2         0.00         0.00      0.00      0.00         0.00    114688.00 
pr2         0.00         0.00      0.00      0.00         0.00    114688.00 
pr2         0.00         0.00      0.00      0.00         0.00    115712.00 
pr2         0.00         0.00      0.00      0.00         0.00    114688.00 
pr2       949.75       885.45      0.00      0.00         0.00    108889.39 
pr2     44844.94     44889.90      0.00      0.00     46080.00       757.18 
pr2     60033.06     60048.05      0.00      0.00     56538.69         0.00 
pr2     55816.36     55803.87      0.00      0.00     61440.00         0.00 
pr2     72003.70     71991.21      0.00      0.00     48128.00         0.00 
pr2     54597.31     54557.34      0.00      0.00     59520.54         0.00 
pr2     54517.38     54557.34      0.00      0.00     61440.00         0.00 
pr2     54597.31     54557.34      0.00      0.00     61440.00         0.00 
pr2     56114.54     56131.86      0.00      0.00     60831.68         0.00 
pr2     54677.25     54687.24      0.00      0.00     61440.00         0.00 
pr2     58354.38     58374.36      0.00      0.00     61212.00         0.00 
pr2     66667.88     66660.38      0.00      0.00     53248.00         0.00 
pr2     54597.31     54557.34      0.00      0.00     61440.00         0.00 
pr2     65483.80     65541.26      0.00      0.00     54272.00         0.00 
pr2     55009.49     54997.00      0.00      0.00     60388.00         0.00 
pr2     55529.08     55549.46      0.00      0.00     61440.00         0.00 
pr2     60352.81     60327.44      0.00      0.00     57344.00         0.00
pr2     51879.44     51904.81      0.00      0.00     50176.00     14336.00 
pr2         0.00         0.00      0.00      0.00         0.00    114566.34 
pr2      1119.12      1088.76      0.00      0.00         0.00    104447.83 
pr2         0.00         0.00      0.00      0.00         0.00    115712.00 
pr2         0.00         0.00      0.00      0.00         0.00    114688.00 
pr2         0.00         0.00      0.00      0.00         0.00    114688.00 
pr2         0.00         0.00      0.00      0.00         0.00    115712.00 
pr2         0.00         0.00      0.00      0.00         0.00    114688.00 
pr2         0.00         0.00      0.00      0.00         0.00    114688.00 
pr2      2717.88      2700.39      0.00      0.00     13312.00     52264.20 
pr2     36371.56     36371.56      0.00      0.00     25600.00         0.00 
pr2     25722.46     25727.41      0.00      0.00     21291.09         0.00 
pr2     14948.31     14933.32      0.00      0.00     25600.00         0.00 
pr2     20943.62     21008.57      0.00      0.00     19456.00         0.00


i.e. there is no read during write. I can set the length of the "write-only period" with the dirty_xxx parameters under /proc/sys/vm, but that does not really buy me anything.

Question: how can I convince the NFS-I/O to read and write at the same time? I am never writing to any file being read at the same time, so there is no risk in simultaneous read/write.

Thanks and Cheers
Bernd

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