[gentoo-user] [offtopic] Copy-On-Write ?

[Helmut Jarausch]

Hi,

sorry, this question is not Gentoo specific - but I know there are many  
very knowledgeable people on this list.

I'd like to "hard-link" a file X to Y - i.e. there is no additional  
space on disk for Y.

But, contrary to the "standard" hard-link (ln), file Y should be stored  
in a different place (inode) IF it gets modified.
With the standard hard-link, file X is the same as Y, so any changes to  
Y are seen in X by definition.

Is this possible
- with an ext4 FS
- or only with a different (which) FS

Many thanks for a hint,
Helmut