Why does FC6 client become unresponsive during NFS write operations?

[Nick Thompson]

My FC6 desktop client becomes unresponsive every 15-30 seconds for 5-15 
seconds during long NFS write operations. My installation is up-to-date as of 
this morning. This occurs with both an FC4 NFS server and another NFS server 
I have running nfs-utils. I can't see any issues in nfsstat on the client:

[root@ratbert nick]# /usr/sbin/nfsstat --nfs
Client nfs v3:
null         getattr      setattr      lookup       access       readlink
0         0% 39        0% 3         0% 16        0% 30        0% 0         0%
read         write        create       mkdir        symlink      mknod
0         0% 476675   99% 2         0% 0         0% 0         0% 0         0%
remove       rmdir        rename       link         readdir      readdirplus
3         0% 0         0% 0         0% 0         0% 0         0% 223       0%
fsstat       fsinfo       pathconf     commit
5         0% 10        0% 0         0% 376       0%

Client nfs v4:
null         read         write        commit       open         open_conf
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
open_noat    open_dgrd    close        setattr      fsinfo       renew
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
setclntid    confirm      lock         lockt        locku        access
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
getattr      lookup       lookup_root  remove       rename       link
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
symlink      create       pathconf     statfs       readlink     readdir
0         0% 0         0% 0         0% 0         0% 0         0% 0         0%
server_caps  delegreturn
0         0% 0         0%

On the server I see nothing wrong:

# cat /proc/net/snmp
Ip: Forwarding DefaultTTL InReceives InHdrErrors InAddrErrors ForwDatagrams 
InUnknownProtos InDiscards InDelivers OutRequests OutDiscards OutNoRoutes 
ReasmTimeout ReasmReqds ReasmOKs ReasmFails FragOKs FragFails FragCreates
Ip: 2 64 2033141 0 0 0 0 0 2033109 1264641 0 0 0 0 0 0 0 0 0
Icmp: InMsgs InErrors InDestUnreachs InTimeExcds InParmProbs InSrcQuenchs 
InRedirects InEchos InEchoReps InTimestamps InTimestampReps InAddrMasks 
InAddrMaskReps OutMsgs OutErrors OutDestUnreachs OutTimeExcds OutParmProbs 
OutSrcQuenchs OutRedirects OutEchos OutEchoReps OutTimestamps 
OutTimestampReps OutAddrMasks OutAddrMaskReps
Icmp: 5 0 5 0 0 0 0 0 0 0 0 0 0 21 0 21 0 0 0 0 0 0 0 0 0 0
Tcp: RtoAlgorithm RtoMin RtoMax MaxConn ActiveOpens PassiveOpens AttemptFails 
EstabResets CurrEstab InSegs OutSegs RetransSegs InErrs OutRsts
Tcp: 1 200 120000 -1 2 205 0 0 1 2031363 1263636 2 0 0
Udp: InDatagrams NoPorts InErrors OutDatagrams
Udp: 1700 17 0 993

Any ideas what I can look at? I need to get NFS running for home directories, 
but the machine using it become unusable when copying big files around.

Thanks,
Nick.