I've also had problems getting "common_server_for_dup" to work in my environment, my duplications would sometimes still use the wrong media server. If you are still having trouble, here is an alternative:
If your backup image is located on disk storage at your DR site and is the PRIMARY or only copy, you can use the command line to specify the media server to use.
1. Create a text file on the master server or media server (any diredctory, it doesn't matter) containing all of the backup IDs you want to duplicate, and call it something like "bidfile.txt". You can use the GUI to list the images in the Catalog and paste it into Excel, or Notepad, or anything that will make it easier to edit. The ONLY text in the file should be the image names, like this:
client1backup.domain.com__1388030438
client2backup.domain.com__1388030439
2. MAKE A COPY OF THAT BIDFILE!! If the duplication job runs, even if it fails, the bdifile will be deleted, so copy it to something like bidfile_backup.txt
3. Execute the following command:
bpduplicate -Bidfile bidfile.txt -dstunit Abisheks_storage_unit -dp Abisheks_tape_pool_name -rl pick_a_retention_level -altreadhost Abisheks_DR_Media_server -L pick_a_logfile_name
Note that the retention level is a NUBMER corresponding to the retention levels defined on the master server's properties; look them up in the "Host Properties" for the NBU master server in the GUI before proceeding!
4. If the duplication fails, check the logfile defined at the end of the command above for the reason (I might have missed a required option). Figure out what needs to be corrected, then copy the "bidfile_backup.txt" back to "bidfile.txt" and retry the operation again.
Note that you can have more than one duplication running, if you have more than one tape drive available at the DR site. Just divide up the list of backups and create more than one bidfile.txt and use a different logfile in each command.
