[Dirvish] Dirvish/rsync thinking partition is 'new'

[Dale Amon]

On Sun, Mar 06, 2011 at 01:28:29PM +0100, Paul Slootman wrote:
> Dirvish's mission is to keep a completely correct backup of the source
> tree. If attributes have changed, they may have been changed because
> things didn't work correctly before, so it's important to have the
> latest image reflect those changes. It's also possible that the changes
> were in error, hence it's also important to preserve the previous image,
> so simply hard-linking the files and updating the owner is wrong.
> Unfortunately the only correct solution is therefore to create a new
> copy of all those files.

Oh futz. Hard links don't allow a new directory entry with different
metadata. I had not thought that all the way through.

> I don't know whether the COW implementation on top of btrfs might help
> in that respect.

You could get enormous savings in back up space if these problems
could be solved. Another is the case where you move an iso or 
rename it. Nothing has changed and yet you suck up disk space like
mad in your dirvish vault.

It's sort of the deduplication problem... if btrfs really does
solve that, it could be a very big win.