NFS "execution time" statistic. Anyone knows what it means?
Hello all,
I'm looking into a performance issues for NFS volumes on RHEL 5.6; the volumes are served from a NetApp NAS device. During times of heavy load on the NFS shares (approximately 6000 ops/sec) we are seeing IO wait times go up. We are using NFSv3 with the following mount options...
rw,intr,nolock,tcp,nfsvers=3,rsize=32768,wsize=32768
When loads are light the nfsiostat command shows the "round trip time" and "average execution" time to be pretty much identical. For example...
op/s rpc bklog 642.25 0.00 read: ops/s kB/s kB/op retrans avg RTT (ms) avg exe (ms) 0.500 2.125 4.250 0 (0.0%) 0.500 0.500 write: ops/s kB/s kB/op retrans avg RTT (ms) avg exe (ms) 19.000 140.505 7.395 0 (0.0%) 0.579 0.618
When under load the "avg exe" value begins to be much longer than the RTT...
op/s rpc bklog 2913.75 44.62 read: ops/s kB/s kB/op retrans avg RTT (ms) avg exe (ms) 129.250 4136.312 32.002 0 (0.0%) 23.567 36.025 write: ops/s kB/s kB/op retrans avg RTT (ms) avg exe (ms) 2211.750 70927.435 32.068 0 (0.0%) 4.050 65.749
Does anyone know what the actual difference is between RTT and Average-execution-time?
Thanks
Nathan