Re: [Bacula-users] More help with DVDs [solved?]

[Richard M. <ri...@ol...>]

On Mon, 2007-02-05 at 16:06 -0500, Andrew Fabian wrote: 
> I've made some progress here.  It appears that in my original 
> configuration, the last session on a disk isn't readable, though bacula 
> thinks that it is written properly.  Here's why I think that, and my 
> solution follows.
> 
> If I run a small, 50 meg backup job twice, then run a 5 gig backup job, 
> my first dvd should contain files like dvd-0001.1 (first 50 meg backup), 
> dvd-0001.2 (second 50 meg backup), and dvd-0001.3 (first part of 5 gig 
> backup).  The second disk should contain dvd-0002.1 (second part of 5 
> gig backup).
> 
> After running a scenario like this, all jobs complete successfully, but 
> if I mount the disks and list their contents, dvd-0001.3 is missing.  
> Furthermore 'dvd-handler /dev/dvd free' shows the first disk mostly 
> empty, minus the first two parts.
> 
That is good to hear.

> The solution, was, as Richard (and the manual) suggested, to use the 
> MaximumPartSize = 800M option to break the 5 gig backup into 800 meg 
> parts.  I'm unclear why this changes the job's outcome, but it does.  
> The last Part on the DVD is readable, unlike with an unlimited 
> MaximumPartSize.
> 
Well I don't know a definitive answer but I wonder if it has something
to do with the layout of the ISO images. I remember that there are
issues with the files over 2gb and there is an issue with the entire
image crossing 4gb. This could explain what you see because that might
make the kernel not able to find the root directory for the final write
and it finds an earlier one that appears incomplete.

Anyway I'm glad that things are working better.

Richard


> - Andy
> 
> Richard Mortimer wrote:
> >> 1) Say we're migrating two jobs, with sized of 6 gigs and 1 gig, to 
> >> DVDs.  Bacula labels dvd-0001, writes the entire disk, the asks for 
> >> dvd-0002.  I insert a new blank disk, run the mount command, and then it 
> >> writes the rest of the 6 gig job to dvd-0002.  That Migrate job finishes 
> >> successfully.  Since the DVD isn't full, it's status is left as 
> >> 'append'.  Bacula now starts migrating the 1 gig job to DVD.  At this 
> >> point, it prompts me, "Please mount Volume "dvd-0002" on Storage Device 
> >> "DVDWriter".  The disk is in there, but I try running unmount and mount 
> >> again.  It prompts me for dvd-0002 over and over again now, and is stuck.
> >>
> >> 2) I'm under the impression that DVDs are read (for restoring data) by a 
> >> normal filesystem mount?
> >>     
> > That is correct.
> >
> >   
> >>   If so, this isn't working on my system, 
> >> because when I mount (mount -t iso9660 -o ro /dev/scd0 /mnt/dvd), it 
> >> mounts an empty, 350k filesystem.  dvd+rw-mediainfo confirms that the 
> >> entire disk has in fact been written to.
> >>
> >>     
> > Did I read it right. You say that it mounts the filesystem ok but that
> > there is nothing in there? After the mount is /mnt/dvd an empty
> > directory?
> >   
> > Before you go much further there are a couple of things that I can think
> > of:
> >
> > 1 - try ejecting the DVD and reloading it. Linux has a "feature" that it
> > doesn't rescan the block device after a write to the DVD. It may be that
> > the mount cannot see the data that has been written. An eject forces
> > things to get rescanned.
> >
> > 2 - One thing that is missing from your config is
> >   MaximumPartSize = 800M;
> > that limits how big each entry (part) written to the DVD is. I don't
> > remember what happens if it is missing but it may be that it will just
> > fill as much as the DVD will take. Hence your first (and second) dvd
> > volumes may have been written without the need to mount the drive to
> > check space and hence bacula didn't notice a problem.
> >
> > Regards
> >
> > Richard
> >   
> 
-- 
Richard Mortimer <ri...@ol...>