Process take long time to write to NFS filesystem.

[unix syzadmin]

Hi,

Users on a RHEL 5.2 run a java process to extract data on a database server
and write them on to a file in NFS filesystem.
The system is a 2CPU (Quad-Core) AMD with 16GB RAM and 2GB swap space.  This
is virtual machine on vmware ESX.

When there is about 2GB of memory free, the process of extracting data and
writing them on to a file in NFS filesystem completes (in 30 minutes).

When the free memory drops to something like 500MB, the process won't
complete in reasonable amount of time.  The system is 90% and more idle, but
the process don't seem to complete. It takes about 7 to 8 hours instead of
30 minutes.

During this time,  any attement to access NFS filesystem like the "df -h" or
cd and ls commands on the NFS filesystem are extremely slow.
If we kill the java process the NFS filesystem returns to normal.


Request yout to suggest or give some pointers on resolving this problem.

If we change the job to write files on local filesystem, we don't see this
problem; irrespetive of the amount of free memory.

The nfs mount options used are (output of nfsstat -m):
Flags:
rw,vers=3,rsize=65536,wsize=65536,hard,intr,proto=tcp,timeo=600,retrans=2,sec=sys

 Thanks.