I have made a fresh install of the diskless machine with the latest ubuntu (11.10) and the problem has gone away.
However, now that you mentioned about big files I noticed in the old diskless file system (ubuntu 10.10) there are many hidden .nfsxxxxxxxxxx files some of them quite big. I suppose they are left overs....
Here are a few examples (the size appears before the date):
115351481 16252 -rw-r--r-- 1 root root 16642048 Feb 26 2011 /mnt1/ubuntu/var/cache/apt/.nfs0000000002a50011000000e2
115351436 16792 -rw-r--r-- 1 root root 17236093 Sep 11 15:57 /mnt1/ubuntu/var/cache/apt/.nfs0000000006e01f8c00000063
115351478 16020 -rw-r--r-- 1 root root 16404288 Dec 20 2010 /mnt1/ubuntu/var/cache/apt/.nfs000000000057c00900000032
115351480 16208 -rw-r--r-- 1 root root 16594500 Feb 16 2011 /mnt1/ubuntu/var/cache/apt/.nfs0000000002a5001200000036
115351483 16704 -rw-r--r-- 1 root root 17102785 May 5 2011 /mnt1/ubuntu/var/cache/apt/.nfs0000000002a5004d00000032
115351460 16824 -rw-r--r-- 1 root root 17283067 Oct 22 07:45 /mnt1/ubuntu/var/cache/apt/.nfs0000000006e01fa40000009d
115351839 16820 -rw-r--r-- 1 root root 17284552 Oct 13 07:26 /mnt1/ubuntu/var/cache/apt/.nfs0000000006e0211f0000001b
115351479 16152 -rw-r--r-- 1 root root 16536128 Feb 2 2011 /mnt1/ubuntu/var/cache/apt/.nfs0000000002a5000f00000026
115351470 16804 -rw-r--r-- 1 root root 17258153 Sep 17 07:51 /mnt1/ubuntu/var/cache/apt/.nfs0000000006e01fae000000bd
115351755 16820 -rw-r--r-- 1 root root 17261588 Oct 5 07:33 /mnt1/ubuntu/var/cache/apt/.nfs0000000006e020cb00000019
115351482 16380 -rw-r--r-- 1 root root 16769594 Apr 22 2011 /mnt1/ubuntu/var/cache/apt/.nfs0000000002a5004c0000001b
115352738 4 -rw-r--r-- 1 root root 1681 Feb 2 2011 /mnt1/ubuntu/etc/.nfs0000000006e024a200000026
115353070 2097156 -rw-r--r-- 1 root root 2147483648 Mar 18 2011 /mnt1/ubuntu/etc/.nfs00000000001b807b00000028
I have made a fresh install of the diskless machine with the latest ubuntu (11.10) and the problem has gone away.
However, now that you mentioned about big files I noticed in the old diskless file system (ubuntu 10.10) there are many hidden .nfsxxxxxxxxxx files some of them quite big. I suppose they are left overs....
Here are a few examples (the size appears before the date): var/cache/ apt/.nfs0000000 002a50011000000 e2 var/cache/ apt/.nfs0000000 006e01f8c000000 63 var/cache/ apt/.nfs0000000 00057c009000000 32 var/cache/ apt/.nfs0000000 002a50012000000 36 var/cache/ apt/.nfs0000000 002a5004d000000 32 var/cache/ apt/.nfs0000000 006e01fa4000000 9d var/cache/ apt/.nfs0000000 006e0211f000000 1b var/cache/ apt/.nfs0000000 002a5000f000000 26 var/cache/ apt/.nfs0000000 006e01fae000000 bd var/cache/ apt/.nfs0000000 006e020cb000000 19 var/cache/ apt/.nfs0000000 002a5004c000000 1b etc/.nfs0000000 006e024a2000000 26 etc/.nfs0000000 0001b807b000000 28
115351481 16252 -rw-r--r-- 1 root root 16642048 Feb 26 2011 /mnt1/ubuntu/
115351436 16792 -rw-r--r-- 1 root root 17236093 Sep 11 15:57 /mnt1/ubuntu/
115351478 16020 -rw-r--r-- 1 root root 16404288 Dec 20 2010 /mnt1/ubuntu/
115351480 16208 -rw-r--r-- 1 root root 16594500 Feb 16 2011 /mnt1/ubuntu/
115351483 16704 -rw-r--r-- 1 root root 17102785 May 5 2011 /mnt1/ubuntu/
115351460 16824 -rw-r--r-- 1 root root 17283067 Oct 22 07:45 /mnt1/ubuntu/
115351839 16820 -rw-r--r-- 1 root root 17284552 Oct 13 07:26 /mnt1/ubuntu/
115351479 16152 -rw-r--r-- 1 root root 16536128 Feb 2 2011 /mnt1/ubuntu/
115351470 16804 -rw-r--r-- 1 root root 17258153 Sep 17 07:51 /mnt1/ubuntu/
115351755 16820 -rw-r--r-- 1 root root 17261588 Oct 5 07:33 /mnt1/ubuntu/
115351482 16380 -rw-r--r-- 1 root root 16769594 Apr 22 2011 /mnt1/ubuntu/
115352738 4 -rw-r--r-- 1 root root 1681 Feb 2 2011 /mnt1/ubuntu/
115353070 2097156 -rw-r--r-- 1 root root 2147483648 Mar 18 2011 /mnt1/ubuntu/