Fedora14: Very very slow NFS write performance

[Terry Barnaby]

Anyone know why the NFS write performance with Fedora14 may be slow (without 
async) ?
I have Gigabit networking which is all working fine and the systems in question
have been running Fedora in various forms for many years.

Writing a single large file across NFS is fine, about: 32MBytes/sec without
async and 51 MBytes/sec with async. However if I untar a 30MByte tar file
that has 2466 files in it into an NFS mounted directory with async it takes 
about 8 seconds but without async it takes over 9 minutes !!

Is this expected ?
If not any ideas what is wrong ?

I am seeing the following:

data.bin binary file 100MB
jpgraph-3.5.0b1.tar tar archive 29MB 2466 files

# Test1, defaults: nfs version 4,
Server /etc/exports:	"/data *.kingnet(rw)"
Client /etc/fstab:	"king.kingnet:/data /data nfs defaults 0 0"

dd if=/tmp/data.bin of=/data/tmp/data.bin bs=102400
32.9 MB/s

dd if=/data/tmp/data.bin of=/tmp/data1.bin bs=102400
66.5 MB/s

time tar -xf /tmp/jpgraph-3.5.0b1.tar
real    9m35.235s

# Test2, nfs version 4, async
Server /etc/exports:	"/data *.kingnet(rw,async)"
Client /etc/fstab:	"king.kingnet:/data /data nfs defaults 0 0"

dd if=/tmp/data.bin of=/data/tmp/data.bin bs=102400
51.3 MB/s

dd if=/data/tmp/data.bin of=/tmp/data1.bin bs=102400
126 MB/s

time tar -xf /tmp/jpgraph-3.5.0b1.tar
real    0m7.938s

# Test3, nfs version 3, async
Server /etc/exports:	"/data *.kingnet(rw,async)"
Client /etc/fstab:	"king.kingnet:/data /data nfs defaults,nfsvers=3 0 0"

dd if=/tmp/data.bin of=/data/tmp/data.bin bs=102400
52.6 MB/s

dd if=/data/tmp/data.bin of=/tmp/data1.bin bs=102400
146 MB/s

time tar -xf /tmp/jpgraph-3.5.0b1.tar
real    0m4.920s

Terry