Jeffrey J. Kosowsky wrote:
> 
>  > And for extra points, figure out which variations could be adapted to 
>  > incremental updates as you might want to do to keep an offsite copy in 
>  > sync.  The blockdevice approach would probably require ZFS with its 
>  > snapshot send/receive functions.  The tarPCcopy approach would need to 
>  > catch all files under directories newer than the previous run - and 
>  > maybe track current directory contents for deletions which is one of the 
>  > Gnutar extensions.
> 
> You need to be careful about hash chain renumbering which could mess
> things up if you are just looking at file names and file modification
> dates. Would gnutar handle this properly without having to run through
> all the hard links? Some of the simpler methods would fail here
> without additional logic.

No, gnutar doesn't have any way to track and propagate renames. It would 
have to delete and copy the pool file contents to the new name - as 
would rsync.  This would leave the pc files connected to the right 
content but no longer associated with the pool.  You could simplify this 
issue by cheating: make the nightly run log the deletes and renames and 
duplicate the actions on the copy, keeping that in sync with creating 
the representation of new link items.  I think star has some sort of 
rename-tracking or inode-following concept in its dump emulation mode 
incrementals but I haven't looked at it all that closely.  It seemed as 
slow as other approaches when I tried it for a full copy, but maybe the 
incremental dump mode would get the subsequent things right.  Unlike 
other tar-alikes, this has to be aligned on filesystem boundaries, but 
that probably wouldn't be a big problem.

-- 
   Les Mikesell
    lesmikesell AT gmail DOT com


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