Jeffrey J. Kosowsky wrote:
>  
> Maybe this is offtopic, but wouldn't it be helpful to have something
> like a Tar+ Xfer incremental method that would make up for tar's
> deficiencies.
> 
> For example if you ran a "find" on the share and combined that with
> the tar data then presumably you would be able to identify which files
> have been moved or deleted (vs. which ones are unchanged). This would
> (in general) not be too intensive either computationally or from a
> bandwidth perspective and would allow Tar incrementals to be "correct"
> (of course it still wouldn't detect files that changed but had an
> earlier timestamp but generally that is a less frequent case).
> 
> Of course if you go too far down this path, you might end up rewriting
> rsync, but at least there might be some low hanging fruit that would
> improve the tar method for incrementals.

Gnutar already has this mechanism with the "--listed-incremental 
filename" option. If the specified file does not exist, a full run is 
done and the file is created containing a list of the directories 
traversed.  If the file does exist, an incremental run is done based on 
the timestamp of the file and ctimes of the target files and including 
the complete contents of any directories that are not listed.  The 
backup uses the 'gnudump' format which contains directory listings of 
all files present at the time of the backup so you can optionally delete 
anything that wasn't there during a restore.

Amanda knows how to use this, but there are some downsides.  During 
incremental runs, the file is modified in place assuming you want 
incremental levels.  If you want incrementals based on the last full, 
you have to copy the file before the incremental to reuse next time. 
Obviously, this requires client-side code to manage the files.

'Star' also has an enhanced incremental mode that works more like dump, 
but it requires runs to be based on filesystem boundaries.

-- 
   Les Mikesell
    lesmikesell AT gmail DOT com


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