Re: [Bug-tar] Trying to figure out why unchanged file gets backed up in level 1 backup

[Joerg Schilling]

"Bret Mckee" <address@hidden> wrote:

> Greetings:
>
> I'm having a problem with incremental backups.  I'm using amanda to
> manage the backups, but this looks like a  gnutar issue to me.
>
> I did the first backup, and of course it did a level 0. I then did a 
> second backup and it did a level 1 backup.  Because I have a large
> /home disk, I back up all the users directories separately.
>
> My home directory (/home/mckee) is about 5GB, and the level 0 seemed
> large enough to have gotten to it all.  The level 1 backup was run
> almost immediately (as part of testing the new install), and virtually
> nothing changed. I was really surprised to see that the level 1 was
> about 500Mb or 10% of the level 0 (I had expected it to be much
> smaller). 

Incrementals made with GNU tar usually are bigger than possible.

Did you try out what the size of the incremental made with star would be?

If you like to do the check, you could do the following:

1)      create a file /etc/tardumps with the following content:

<mount point>                       <level> timestamp
            ^^^^^
        filename, <TAB>, followed by spaces

The timestamp is a UNIX time in microsecond resolution.

e.g. like this:

/mnt                                      0 1092744351.392399 Tue Aug 17 
14:05:51 2004

2)      run a level 1 dump like this:

        star level=1  -nullout -wtardumps -cPM -dump -sparse -C /mnt .  

If you use the sema time stamp as you used with the GNU tar level 0 dump,
you will then see how big an incremental dump for the same fs would become if 
you use star.

ftp://ftp.berlios.de/pub/star/alpha/

Jörg

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