NFS mount: iostat shows %b=100 and high kr/s for long time and but dtrace show low file io

Hi Gurus,

an Java application is unable to start due to timeout. it uses NFS extensively for both binary and data storage. iostate shows %b=100 consistent,  kr/s of 2000-2900 and r/s of 1.9 -4 on the NFS mount over 2 hours 15 minutes before it failed with timeout error. there is no other application running on the same server.

below is a typical sample from that period:

Wed Nov  9 18:04:44 2016

                    extended device statistics

    r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device

    2.4    0.0 2457.7    0.0  0.0  1.0    0.0  416.7   0 100 devcnfs12:/export/algo/algo

so we can estimate that roughly 7.5GB of data was read from the nfs file system for a 53-minute span.