NFS Blocksize Optimizations

I decided to redo the NFS setup I previously had on my ol’ Itanium2 machine.

Standard disclaimer: These tests were run with purposeful cache prevention techniques so that caching would not make all subsequent tests faster, yada yada, I am not retarded.

Specs:
2x 1.5GHz Itanium2 processors
10GB ECC DDR
3x 74GB 15k RPM U320 SCSI drives in RAID5
Gigabit ethernet

I am somewhat confused as to why the NFS write performance is so appalling, while the read performance approaches the theoretical maximums of a gigabit ethernet connection.
Any advice on improving write performance over NFS would be much appreciated.

(Graph is here if you’re reading this post without images)