There have been several posts recently about various aspects of
duplication.  Here
is a description of the way we do things here which I hope others will
find useful.

        To start with, let's make some observations about the way NetBackup
handles
the duplication process:

        (i)     Duplication jobs seem to be "invisible" to other activities 
such as
                backup and restore.  For example, dup jobs don't show up in the
                xbpmon screen.

        (ii)    Because of this "invisibility", you can get into trouble if you
                have dup jobs running when you want to do a backup as the backup
                process will think there are storage units / tape drives 
available
                when in fact there are none (and so you'll get a media mount 
timeout
                causing the job to re-queue -- as long as the dup run finishes 
during
the
                backup window, the backup job will complete but you will, of 
course,
get
                lots of error messages / emails which is not very satisfactory.

        (iii)   If you had multiple (say 2) libraries, you could mark the S/U
representing
                one of them as "On Demand Only".  Then, assuming your class(es) 
use
"Any
                Storage Unit", they will skip this one and not run into the 
problems
of (ii).

        (iv)    The trick here is to find a way to "logically" subdivide a 
library
into
                multiple storage units so that multiple dup runs can take place 
at the
                same time.


After lots of head-scratching and calls to the Veritas support desk, the
recipe we
use is (starting with a 4-drive ATL P3000 library configured as a single
S/U):


                (a)     Change the S/U S0 to have 2 drives instead of four

                (b)     Create two new S/U's, each with a single drive.  Make 
the
                        drive type be DLT2

                (c)     In device manager, stop the daemon then use Update Drive
                        to change the density of two of the drives to be DLT2 
and
                        then restart the daemon


                What you then have is:


                S0              contains        2 dlt drives

                S1              "               1 dlt2 drive

                S2              "               1 dlt2 drive


                Now S1 and S2 can both be specified as "destination storage 
units" in
the
                Images->Duplicate panel, i.e. both can be active at once.  So, 
our
                procedure is to generate the list of backup id's to be 
duplicated and
                then select half (ish) to use S1 and the rest to use S2.

                This, of course, will use up all 4 drives (since the 2 in S0 are
needed
                to read the originals) ... for this reason, we're adding a 
fifth drive
                which can be used for backups / restores while duplications are 
in
process.

Let me know if this isn't clear.


Cheers,

Richard.