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/proc/mounts shows rsize has been negotiated to 1mB
Have you tested the same thing with a Linux NFS server?
The CentOS 5.x kernel has a maximum server [rw]size of 32Kb, so you would need to use something with a more recent kernel to get [rw]sizes to be 1Mb.
Haven't tried with a linux server, will do. One thing tho, we are still mostly running old Fedora Core 6 installs (migrating to CentOS), which also negotiated rsize to 1mB with the same NFS server, and they don't have the problem :
$ dd if=toto of=/dev/null bs=1024k 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 1.44039 seconds, 72.8 MB/s
$ cat /etc/redhat-release Fedora Core release 6 (Zod)
tail -1 /proc/mounts nfs1:/local/users /users nfs rw,vers=3,rsize=1048576,wsize=1048576,hard,intr,proto=tcp,timeo=600,retrans=2,sec=sys,addr=nfs1 0 0
The setup and hardware is strictly identical to the CentOS environment. (we've installed both distros on the same servers, just to be sure).
Network traces don't show anything special, no fragmentation or delays. The only odd thing as I mentionned is that it's the client which is waiting a long time between requests. Wonder what's happening there. Well I'll try with a linux NFS server see if it changes something, will post here if we figure it out
Regards,
Alex