[Wlug] bacula

[Frank Sweetser]

On Mon, Sep 04, 2006 at 03:11:14PM -0700, Mike Leo wrote:
> i have a 35/70Gb DLT drive with IV tapes, but I am only getting less than 30
> gigs' per tape.
> 
> my bacula-sd.conf lists " Media Type = DLT"....if this is not accurate, could
> bacula think I have only a 15/30Gb drive?  Should it read DTL7000 or
> something?

Bacula doesn't actually parse the media type - it's nothing more than a unique
identifier string that bacula uses to determine what volumes can be read by
what drives.  You could call file volumes "blue", DLT tapes "red", and DVDRs
"green" and it would work fine.

Bacula doesn't try to pre-determine the amount of space available on a tape.
It just writes until the drive reports that it's hit the end of media, re-reads
the last succesfully written block to make sure it got there okay, marks the
volume full and asks for another one.

The fact that you're getting about 30G of data per tape implies that you have
hardware tape compression off.  I believe the 'mt' command will tell you the
compression status - the online manual has an example.  The other 5G or so is
probably taken up by volume metadata, such as the volume label and file
attributes.

> Also, does bacula compress naturally or do i have to tell it too?

No, you have to explicitly enable gzip compression if you want to use it.  It's
typically reccomended to use drive hardware compression instead, though, as 
   a) drive hardware compression is usually faster, especially on older machines,
and
     b) it's possible to run into file daemon incompatabilities that can make it
difficult to restore data, especially if you're trying to restore the data onto
a different machine that the one it was backed up on.

-- 
Frank Sweetser fs at wpi.edu  |  For every problem, there is a solution that
WPI Network Engineer          |  is simple, elegant, and wrong. - HL Mencken
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