Re: [Bug-tar] question RE incremental backups

[Phil Schumm]

On Oct 10, 2008, at 4:01 AM, Sergey Poznyakoff wrote:
> > OS X 10.5 comes with version 1.15.1 pre-installed, patched by Apple  
> > to handle HFS extended attributes and resource forks.
>
> Just for your information, the latest stable version of GNU tar is  
> 1.20 and the list of changes and bugfixes between 1.15.1 and 1.20 is  
> pretty long, and quite a few of them address incremental backups.   
> In particular, 1.20 stores more meta-information in its incremental  
> dumps which avoids many cases of superfluous dumps (i.e. adding  
> files that did not modify since the last dump). I would advise to  
> upgrade to that version, if it weren't for the fact that you need  
> some third party patches (by the way, are they available  
> somewhere?).  In particular, the first two problems you mentioned  
> (superfluous dumping of files and failing --verify with >0 level  
> dumps) are fixed in 1.20.
>
> > --exclude-from option, the time required for the comparison blows  
> > up.  This suggests that GNU tar is iterating through all of the  
> > files listed in the --exclude-from file over and over, rather than  
> > storing them in a hash table and looking for matches that way.
>
> Yes, for the time being it is so.  There is, however, an ongoing  
> work on that subject.


Sergey,

Thanks very much for your reply.  The Apple patches are available  
online here:

    http://www.opensource.apple.com/darwinsource/10.5.5/gnutar-441/

however I believe they'll require a bit of work to bring them in line  
with 1.20, and I'm not competent to undertake that.  I believe I'll  
try installing 1.20 (we may be able to get by without the resource  
forks and extended attributes in some cases), and I'll also inquire  
with Apple about their plans to upgrade the version they distribute.


-- Phil