[Bacula-devel] Re: [Bacula-users] Backing up to mounted UDF images

[Kern S. <ke...@si...>]

Hello,

I'm sending this to bacula-devel, which is a more appropriate
list.

On Sun, 2003-10-26 at 03:34, John Barrett wrote:
> I'm looking very hard at creating a kernel driver module/user-space daemon
> setup that would allow emulating a tape device -- my first planned daemon
> would be targetted at simulating a tape/autochanger with a dvd-rw juke. I've
> been looking at the char-device code out of "srfs" (a prototype filesystem
> that uses a user-space caching daemon) for handling the link between the
> kernel and the daemon, and the scsi ST code as starting points for the
> package.
> 
> That much would handle the tape read/write/ioctl interfaces -- i just need
> to know a little more about what the autochanger device should look like to
> any application using the driver and I can get started creating the driver
> interface presented to the application.

Bacula's autochanger support works by calling a script, which in
turn calls the mtx program, which uses the generic scsi driver.
The script massages the mtx output and presents it go Bacula
in a much simpler format. The details of the Bacula-script
protocol is defined at the end of the following chapter:

 http://www.bacula.org/html-manual/autochangers.html

Best regards,

Kern

> 
> The idea I'm going for here is that a config file would define the logical
> topology presented to the backup application, and provide the mappings from
> that logical topology to the physical media. For instance, bacula may be
> presented with a 500 tape changer, with each tape holding 500mb of data, and
> that mapped to a 100 disk dvd-rw juke with 5x500mb volumes per disk.
> 
> This would be my first linux device driver (though I have done drivers for
> other operating systems) and I would be interested in collaboration if
> anyone has an interest in working on this idea with me.
> 
> ----- Original Message ----- 
> From: "Tuomas Jormola" <tjo...@cc...>
> To: <bac...@li...>
> Sent: Thursday, October 23, 2003 10:59 PM
> Subject: [Bacula-users] Backing up to mounted UDF images
> 
> 
> > Hello,
> >
> > I would like to use Bacula to backup files on the machines on my home
> > network. My server has plenty of diskspace on a RAID5 volume that I'd
> > like to use as a primary backup space. But I'd like to archive the
> > backups on DVD+RW disks every now and then at will just in case (once a
> > month, perhaps).
> >
> > The easiest way to achieve this would probably be to create a file
> > storage pool with bunch of volumes with Maximum Volume Bytes option set
> > to near 4.7GB (the amount of data a DVD disk can hold). When I want to
> > burn the data to disks, I would have to create images out of the volume
> > files using eg. mkisofs and then burn the image using some DVD burning
> > application. What's wrong with this approach? Many error-prone manual
> > steps.
> >
> > What I would like to achieve is this. Unlike ISO9600 filesystem used on
> > CD-ROMs, you can use UDF filesystem besides ISO9600 with data DVDs. UDF
> > is rewritable just like ext2 etc. There's a read/write driver for UDF
> > in Linux 2.4 kernel so you can mount UDF images on a hardisk using the
> > loopback device and copy from and to the image and delete stuff. I'd
> > like to create a pool of UDF images on the filesystem on the hard disk
> > and then mount images somewhere and instruct Bacula to store its
> > volumes as 4.7GB files in the mount point of the images. There's a tape
> > autochanger support in Bacula. I thought one could use this facility to
> > pick the appropriate pre-made UDF image or create a new one if no
> > correct image was available and mount or umount it when needed (I have
> > about 30GB worth of data to backup so I'd better prepare about 10 or
> > more images and use these in round-robin fashion). I created a test
> > script based to mtx-change to run as Changer Command just to see what
> > kind of values %o, %f, %j and %v variables would get when the script
> > was run in my environment. I never managed to get it run if Archive
> > Device in bacula-sd.conf was set to a directory. Neither did it run
> > when it was set to /dev/null. Autochanger is set to yes. Creating a
> > label fails with /dev/null as device, of course, and at that point I
> > gave up and decided to ask your help. Would this kind of hybrid between
> > file storage and removable media ever work? If not, perhaps it would be
> > an idea worth evaluating if it should be implemented, since with all
> > these new sub-$200 IDE DVD-burners, this method would be a very
> > attractive backup solution for smallish non-mission critical sites.
> >
> > Another solution that might work would be using FIFOs. This would
> > probably require adding options like Pre Read FIFO Command that would
> > mount correct UDF image and Post Read FIFO Command which would mount it
> > after the script at the other end of the FIFO would've written the data
> > to a file in the mount point.
> >
> > Any other ideas or suggestions from users who backup their stuff on
> > DVDs/CD-Rs using Bacula?
> >
> > Best Regards,
> > -- 
> > Tuomas Jormola <tjo...@cc...>
> >
> >
> >
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> 
> 
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