NFS Performance

[James Kimble]

2 servers: an L1000 (1 cpu) and an L2000 (2 cpu) both HPUX 11. Identical kernels, and latest NFS performance patches. When running i/o tests with 4kb records the i/o rate on the L1000 is approx 80,000kb/sec. while the L2000 is showing approx 8,000kb/sec!! Once the record size increases to >= 8kb. then the L2000 starts to i/o at 100,000 - 180,000 kb/s. Any ideas as to why the 4kb record kills the L2000?

[Brian Hackley]

Scott,
That's a pretty complex set of circumstances you've got there. You meantion terms like "record size" so it sounds like you're using a COBOL program to write from an application.
You can probably "drill down" a bit further to find out what is actually the root cause of the performance differential. A smaller record size means that the UDP packets being sent by NFS are probably smaller in size on the network. However it could also be that the smaller record size is causing a bottleneck in the disk subsystem on the NFS Server.
Take a look at the NFS Performance assessement writeup KBAN00000261 in for some tips. Specifically you might want to use ttcp or netperf to determine the ability to send UDP Packets of various sizes up to 8K from the NFS client to the NFS Server.
Hope this helps a little,
Brian Hackley