Re: [Bug-tar] question RE incremental backups

[Sergey Poznyakoff]

Hi Phil,

> 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.

Regards,
Sergey