On Fri, 2006-03-24 at 11:04, Tomasz Chmielewski wrote:

> >  > So, in theory, it should be enough to make just one full, initial 
> >  > backup, and then only incremental backups.
> >  > 
> >  > Or do I miss something here?
> > 
> > one reason (there may be others) is that incrementals don't account
> > for the removal of files.  if a full contains a file that is later
> > removed, it will always appear in that "filled" view, even after
> > the file is gone from your system.  so full backups are necessary
> > to reestablish a true image of your current contents.
> > 
> > (this is with tar -- rsync incrementals may actually remove deleted
> > files.  i don't use rsync.)
> 
> So with rsync it shouldn't be an issue, right? Could anyone comment on that?

They have different issues.  I'm not sure about that particular one.
Tar/smb backups use only the file timestamps to decide what to
take in incremental runs and will thus miss files in a new
location because a directory above was renamed and in at least
the smb case, files that are back-dated by copy mechanisms
that preserve the original timestamp (unzip, etc.).  These
omissions accumulate until you do the next full.

Rsync can always identify new or moved files compared to your
backup, but it will always tranfer the changes made since the
last full, so the size will keep increasing as you repeat
incremental runs.  Rsync also bases comparisons on the file
size/timestamp during incremental runs but does block checksum
comparisons of everything for fulls.

In all cases, identical files are collapsed into hard links
to the pool copy, so the only down side of full runs is the
extra bandwidth for the tar/smb copies and extra time for rsync. 

-- 
  Les Mikesell
   [EMAIL PROTECTED]




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