Hi list,
We've had an interesting NFS performance issue with the following setup. Clients : CentOS 5.5, kernel 2.6.18-194.el5 Server : Solaris 10 kernel Generic_142901-08
Reading a file (not cached) with dd : dd if=file1 of=/dev/null bs=1024k count=100 performance is around.. 700 kB/s !
/proc/mounts shows rsize has been negotiated to 1mB
If we force rsize to a smaller value, 32kB, the problem goes away and we're back around 70/80 mB/s read performance.
Wiresharks show something interesting in the first (slow) case: It seems that the NFS client is "waiting" between requests:
1473 11.756852 client.net nfs1.net TCP 868 > nfs [ACK] Seq=9345 1474 11.757888 nfs1.net client.net RPC Continuation 1475 11.797837 client.net nfs1.net TCP 868 > nfs [ACK] Seq=9345 1476 11.798877 nfs1.net client.net RPC Continuation [....]
Notice how the server replies within about 0,001s, but the client appears to be waiting 0,04s before asking for the next bit. (we captured the traffic from the client). This pattern repeats for the whole exchange
It's likely we missed something, can't figure it out.. has anyone seen this before ?
Cheers,
Alex