Alexandre Lecuyer wrote: > 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 > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos > Well, it's been a long time since I've done troubleshooting on large NFS networks, but here's an idea... Are you seeing any kind of packet loss/retransmissions? Take a look at netstat -s. When I last did this work it was with NFS over udp, but I think retransmitted packets will cause more performance loss with large packet sizes. I used to find machines with broken ethernet interfaces that would cause these kinds of problems. Nataraj