Hi Thomas,

> > Your web view would become inconsistent (e.g. deleted files becoming
> > visible again).
> Ok, this seems to be a case we forgot ;-(
> But if this doesn't matter to us, is it then okay to delete any backup?
> Do the GUI and the creation of new backups work and don't throw errors?
> 
> By the way: How are deleted files represented?

They are marked as deleted in the fattrib files.

> I argue they are just missing in the respective backup hardlink tree.
> So if you delete the backup hardlink tree, the "holes" disappear?

There are a lot more cases to consider. I wouldn't risk getting an
inconsistend view of the backups... see below.

> > > In both cases only changed/new files use disk space according to the
> > > hardlink concept of BackupPC.
> >
> > Yes. Fulls need some more space because they are completely filled, that
> > is, all directories contain hardlinks to all the files, whereas
> > incrementals only contain hardlinks to new and changed files -
> > filesystem-wise they've got holes which are filled by the CGI.
> But this is just management space (directories and their dentries) --- which 
> uses of course some inode and data space. No additional data space and inode 
> space is needed for the real files in full backups compared to a incremental 
> backup. Is that correct?

Yes.

> If this is the case we think about doing full backups all the time.
> So deletion of backups is ok then too.

I wouldn't do that. You could use the $Conf{IncrFill} option. Then each
incremental is filled up and does not depend on previous incrementals
(except for doing actual backup).

What are you trying to achieve, after all? Please tell us about the
problem you're trying to solve - there might be easier approaches.
BackupPC automatically deletes too old backups and takes care for
keeping/deleting depending incrementals as long as neccessary.

> > > We have also detected, that in some cases incremental backups need much
> > > more time than full backups (factor 3-5) This sounds odd to us.
> >
> > What transfer method are you using?
>
> rsync over GBit networks between Linux machines and also between MacOS 
> machines. In both cases that effect happens.

That's strange. Please have a look at the server's and client's load
during incremental backup - maybe something is running on either of them
which takes a lot of CPU and/or network and/or memory...

HTH,

Tino.

-- 
"What we nourish flourishes." - "Was wir nähren erblüht."

www.lichtkreis-chemnitz.de
www.craniosacralzentrum.de

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