[rdiff-backup-users] Re: How much metadata to store

[Gregor Zattler]

Hi Ben,
* Ben Escoto <address@hidden> [05. Dez. 2002]:
> >>>>> "GZ" == Gregor Zattler <address@hidden>
> >>>>> wrote the following on Tue, 3 Dec 2002 15:42:31 +0100
>   GZ> a) all metadata is stored but actually mungling metadata on the
>   GZ> mirror side is an option
> 
> Sorry, what does this mean?

[Sorry for my poor english.]  The store-all-meta-data idea should
provide the ability to use compressed mirrors or (as i pointed
out) could be used to *later* move the rdiff-backup (mirror plus
diffs) to a different file systems which probabily miss some
features the original file system provides.  

To use this new flexibility the file names on the mirror side must
be altered.  If this happens in backup-time one cannot easily use
the mirror with standard unix file manipulation commands (cp, mv,
diff...) because the file names differ.

If altering file names in order to provide for compressed,
encrypted or other file systems was an option --> one could
use rdiff-backup the old way but later decide to compress encrypt
or move the rdiff-backup (mirror plus diffs).  The stored meta
date would provide the information to do so when need arises.


Example:

One rdiff-backups a ext2 file system to another ext2 file system.
Here altering file names is not needed.  rdiff-backup stores all
meta data.  From time to time one uses the mirror to get the very
last version of a accidentily deleted file, no special tools
needed, only cp .../from/xxx .../to/xxx .  The meta data is never
used until:

Later the need arises to move the backup to a vfat file system.
But there are file names which differ only in upper/lower case
letters. 

rdiff-backup --magic-move-backup from-old-rdiff-bacup-location 
to-new-rdiff-backup-location

rdiff-backup recognises a vfat file system.  Files wich names
would collide in vfat get changed to be different and the new
file name(s) get stored in the meta data file.

One uses this new location as if s/he had used this from the
beginning, doing further backups, restores...

Next Chrismas management spends new hardware.  One then moves the
backup to a new reiserfs partition:  rdiff-backup de-mungles the
file names according to the meta data file...


Mhm, reconsidering.  I wrote:

>   GZ> a) all metadata is stored but actually mungling metadata on the
>   GZ> mirror side is an option
>   GZ> 
>   GZ> and/or
>   GZ> 
>   GZ> b) rdiff-backup could reproduce a mirror for a given file system
>   GZ>    with as much metadata provided by this file system as
>   GZ>    possible.

This is no "and/or" but only "and".

I wrote:
>   GZ> I see this would add more complexity but also more flexibility.

;-]


Hope i was more understandable.

Ciao; Gregor