you can read the post here...
http://www.mobiphil.com/?p=23

Hello, tried to investigate why nfs is slow on ubuntu, but no result
so far... writing speed towards the server is horribly low. I made the
following experiments

1. Measured the ip speed with iperf in both directions between the
client and server.

on the server:

xxx@yyyyyyyyy:~$ iperf -s
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Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
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[ 4] local 192.168.12.5 port 5001 connected with 192.168.12.11 port
56444
[ 4] 0.0-10.0 sec 753 MBytes 630 Mbits/sec


on the client

uuuuu@qqq:~$ iperf -c 192.168.12.5
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Client connecting to 192.168.12.5, TCP port 5001
TCP window size: 16.0 KByte (default)
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[ 3] local 192.168.12.11 port 56444 connected with 192.168.12.5 port
5001
[ 3] 0.0-10.0 sec 753 MBytes 631 Mbits/sec

so the transfer rate is quite good (630Mbits/sec) for a Gbit card on
both side as the server has a slower PCI.

2. Copied a 100MByte file from the server to the client, it took 1.6
sec

3. copied a the same 100MByte file from the client and it took
60sec!!! so 10 times slower!!! Cannot beleive.

Here is the line from /etc/fstab for the /home folder

192.168.12.5:/XXXXXX/home /home nfs4
auto,rw,nodev,sync,_netdev,noatime,proto=tcp,retry =10,rsize=32768,wsize=32768,hard,intr
0

4. By changing the sync parameter to async there was some significant
improvement, but still far from perfect copying from the server
remained 1.6 sec, and copy to the server dropped to 3.6 sec. The same
copy on the server, locally takes 1.7 sec.

This means that copying through nfs is twice slower than a local copy
without having network bottleneck.

4. Copying 1000 files of 100kbyte from server to client took ~3sec,
but back to the server 45secs!!!!! This is really painful. This made
it clear, why programs like firefox slowed down since the nfs home.
Firefox writes several small files quite often, so

5. And now some comparison about (half) alternatives. Copying with scp
the same 1000 files to the server took 12secs, so almost a quarter of
the time spent with nfs.

Important to mention that there is no router between the computers,
they are connected with a cat6 cable (gigabit ethernet).

Any suggestion if this copy time could be decreased?