When specifying a group label, sometimes NetVault will use a blank tape even though there are already tapes in that group.
For more information on this topic, please see the Module 3 Advanced Administration Part One-Web-based Training
First, NetVault will examine the drives for a tape it can use. It will favor a tape in the drive over any tape it must move to a drive.
Second, NetVault will use tapes that are already labelled and have space available before it uses a blank tape. By default NetVault will leave the last tapes that were used or blanked in the drives.
If multiple jobs run at the same time and there are multiple tape drives that the job can write to, it will load a tape in each drive so it can do the backups simultaneously. For example if you have 10 jobs that will write to the incremental group and 4 tape drives, it will write to at least 4 tapes even though all the backups may fit on one tape. You can prevent this from happening by configuring all the jobs in the target tab to only use 1 drive, so that only one job can run at a time. Of course limiting all 10 jobs to one drive will increase the time, or 'backup window', needed to complete all ten jobs versus allowing the jobs to write to all 4 drives simultaneously.
Last, NetVault Server will reject a tape of a different format type. On Windows, tape format type is MTF, and on UNIX/Linux, it is CPIO. This last scenario will be an issue only if the NetVault Server was migrated to a system with a different OS family.
