The disk0: is shared by all context.
1Mb is reserved and 10Mb available for all contexts.
Virtualization just prevents one context to access files from another context.
The 9Mb come from another context.
switch/Admin# dir disk0: | i used
4381696 bytes total used
switch/Admin# changeto User2
switch/User2# dir disk0: | i used
4381696 bytes total used
switch/User2#
As can be seen from above, the bytes used are he same for all contexts.
Gilles.