Hello,
On 1/4/2006 11:03 PM, Mario Ohnewald wrote:
Hello List,
On Fri, 2005-12-30 at 20:54 +0100, Arno Lehmann wrote:
Hello,
On 12/30/2005 2:51 PM, Mario Ohnewald wrote:
Hello List,
i would like to back up my files to DVD-RAM.
I simply format my DVD-RAM with: mkfs.ext3 /dev/hdd and then i should be
able to use it.
Okay...lets say you use a tape device. Then Bacula writes to that
device/tape until its full, sends a email/message asking for a new tape
and constantly tries to mount/carry on.
That must be possible with DVD-RAM, too.
Where is the problem? I dont get it.
Basically, tape != disk. A tape is positioned to a certain
blockposition, most often EOT or BOT, and then data is written to it
sequentially. No files, file names, inodes, or anything except for
abstract EOF marks which have no implicit meaning for the tape data
itself. Finally, the tape drive and the OS, report an error when the
tape is full (usually, they already report an error when the tape is
_almost_ full). On a DAV-RAM disk, you put a filesystem. Into this, the
file system driver (OS) puts files which are accessed using names. You
can't simply open the DVD-RAM, position and write until the driver
reports the disk to be full.
What you describe - Bacula fills media and requests another one - is a
much more abstract process. Mapping that high level operation to the
underlying OS and hardware requires about 140.000 lines of C code...
That should work in theory, shouldn´t it?
Yes, in theory, as long as theory means the scenario you present hasn't
much in common with reality :-)
You should refresh some detail knowledge:
- How character devices (tapes) and block devices (disk, DVD-RAM) are
used. Especially sequential operation and everything beyond that via
IOCTLs vs. file systems, block positioning and file I/O at a rather
abstract level.
- the way DVD backups are handled in Bacula now. In my opinion, the
manual section, although short, gives some basic knowledge.
Understanding the dvd-handler script afterwards should give you
everything you need to outline a procedure for DVD-RAM use. (Remember,
this would not be very difficult IMO).
Or, of course, search the bacula-devel list archives for all the
discussion concerning DVD-writing. There are some details mentioned in
the discussions.
Arno
Thanks, Mario
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