Hi Peter,
My envionment looks like that:
NFS ServerïSuse9 Enterprise NFS ClientïRedhat AS3.0(kernel 2.4.21)
I made a ramdisk and export it with nfs
Server and Client are connected with 1000Mbps
mount the ramdisk on the client with parameters: -t nfs -o rw,noac
then test with iometer and the parameters are: Outstanding IO is 32, transfer request size is 512, sequential write
the result is about 300KB/s, iops is about 600
with dd test i find the delay most cost at the server.
i agree with Avi that "if the NFS client has no (or low) concurrency, then write gathering would reduce preformance"