MacからNFSが不安定

先日、NFSサーバを立ててmacからマウントして利用していたが、どうにも不安定。よく固まるうえに、umount -fでもアンマウントできない。極めつけに、ファイルコピー中に突然OSXが落ちるというｗｗｗ
dmesg見るとエラー出まくってるし、、、　ふーむ、さてはて。

nfs_mount_state_in_use_end: error 10025, initiating recovery for 192.168.20.1:/, 0x1
nfs recovery started for 192.168.20.1:/, 0x2
nfs_recover: 10033, need reopen for 502 0xffffff801c188340 0x0 ._test.dat
nfs recovery completed for 192.168.20.1:/, 0x2
nfs_mount_state_in_use_end: error 10025, initiating recovery for 192.168.20.1:/, 0x2
nfs recovery started for 192.168.20.1:/, 0x3
nfs_recover: 10033, need reopen for 502 0xffffff801c188340 0x0 ._test.dat
nfs recovery completed for 192.168.20.1:/, 0x3
nfs_mount_state_in_use_end: error 10025, initiating recovery for 192.168.20.1:/, 0x3
nfs recovery throttled for 192.168.20.1:/, 0x3
nfs recovery started for 192.168.20.1:/, 0x4
nfs_recover: 10033, need reopen for 0 0xffffff801c188340 0x0 ._test.dat
nfs recovery completed for 192.168.20.1:/, 0x4
nfs_mount_state_in_use_end: error 10025, initiating recovery for 192.168.20.1:/, 0x4
nfs recovery started for 192.168.20.1:/, 0x5
nfs_recover: 10033, need reopen for 502 0xffffff801c188340 0x0 ._test.dat
nfs recovery completed for 192.168.20.1:/, 0x5
nfs_mount_state_in_use_end: error 10025, initiating recovery for 192.168.20.1:/, 0x5
nfs recovery throttled for 192.168.20.1:/, 0x5
nfs recovery started for 192.168.20.1:/, 0x6
nfs_recover: 10033, need reopen for 502 0xffffff801c188340 0x0 ._test.dat
nfs recovery completed for 192.168.20.1:/, 0x6
nfs_mount_state_in_use_end: error 10025, initiating recovery for 192.168.20.1:/, 0x6
nfs recovery started for 192.168.20.1:/, 0x7
nfs_recover: 10033, need reopen for 502 0xffffff801c188340 0x0 ._test.dat
nfs_recover: 10033, need reopen for 502 0xffffff801c188630 0x0 test.dat
nfs recovery completed for 192.168.20.1:/, 0x7
nfs server 192.168.20.1:/: resource temporarily unavailable (jukebox)
nfs server 192.168.20.1:/: dead
nfs4_renew_timer: error 6
nfs4_renew_timer: error 6, initiating recovery
nfs delegated state claim error 6, state lost, 502 ._test.dat
nfs: state lost for 0xffffff801c188340 0x2 ._test.dat
fs_vnop_close: error 6, 502 ._test.dat
nfs4_delegation_return, error 6 ._test.dat
nfs server 192.168.20.1:/: resource temporarily unavailable (jukebox)
nfs_vnop_open: error 6, 502 ._test.dat