A few days ago I noticed that NFS performance between a web server node and NFS server went down by 50%. NFS was optimized and the only thing was updated Red Hat kernel v5.2. I also noticed same trend on CentOS 5.2 64 bit edition.
NFS server crashed each and every time web server node tried to store a large file 20-100 MB each. Read performance was fine but write performance went to hell. Finally, I had to rollback the updates. Recently, while reading Red Hat site I came across the solution.
Updated kernel packages that fix various security issues and several bugs are now available for Red Hat Enterprise Linux 5:
* a 50-75% drop in NFS server rewrite performance, compared to Red Hat
Enterprise Linux 4.6, has been resolved.
After upgrading kernel on both server and client my issue resolved:
# yum update