Re: DVD-R as backup medium: growisofs + udftools
"Giuseppe \"Cowo\" Corbelli" <cowo@lugbs.linux.it> wrote:
> Joerg Schilling wrote:
> >> I'm trying to backup a couple of GBs upon a DVD-R using Plextor PX-810SA,
> >
> > What drive is this? Is this a Lite-ON?
>
> Plextor PX-810SA
This is on the label, but who did make the drive?
> >> To start I thought about using packet writing / udftools. By reading
> >> documentation, it states that I have to
> >
> > Wny?
>
> I wanted to mount the media as rw and give its mountpoint to flexbackup as
> 'standard' directory.
Dealing with Write once media is not simple and many use cases do not match.
Another problem is the filesystem. I am not sure whether UDF is the right
filesystem. I did not have the time to check UDF but I suspect that
it is worse than my wofs (designed in 1989) which is the first 100% Copy on
Write filesystem. From my design and implementation I know the limitations..
If you cannot describe the exact behavior of the backup program it is hard to
impossible to tell whether the software is compatible with COW filesystems on
Write once media.
> >> dvd+rw-format -force /dev/sr0
> >>
> >> for RW media only, so I guess this is not applicable to -R, right?
> >
> > Why do you ike to do this at all?
>
> Just quoting the documentation :-) I'm a newbie in DVD recording world.
Documentation claims a lot. Once people check reality, things in most cases
look different.
> > Why don't you just write using mkisofs and cdrecord?
>
> Definitely next step but follow this:
> <ideal world>
> mount -o rw /dev/sr0 /mnt/x
> flexbackup writes to /mnt/x directly using udf/packet
>
> <real world>
> flexbackup writes to a directory
> mkisofs /directory |cdrecord
>
> In real world I need to make room for temporary backup files, which I thought
> I could avoy
It is _impossible_ to do correct backups without additional disk space.
If you like to do backups 100% correct, you need filesystem snapshots.
After you created a snapshot, you run mkisofs -print-size, then you run
mkisofs /directory |cdrecord tsize=xxx.
Before you start using other software for backups, you need to check whether
the backup works at all. If you make e.g. incremental backups from full
filesystems using star, this has been verified to work. If you use anything
based on GNU tar, you should know that there are many bug reports against
incremental restores with GNU tar that never have been verified.
Jörg
--
EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
js@cs.tu-berlin.de (uni)
schilling@fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/
URL: http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily
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