If the file is open and being modified it should be backed up even though changes are being made to it. Most software packages take a snapshot of the file for backup but any changes made after the snapshot are not backed up until the next time the backup runs. On Windows, files can be opened for exclusive access, preventing snapshots from being made. Typically, these files need to be made quiescent before backing up. Before choosing a backup software package, be sure it performs this function before backing them up.
Most software packages do.
This is because they auto-discover most hardware on boot up and install the appropriate device driver. Check your operating system manuals to see if this is the case. This should be saved offsite along with your disaster recovery backups. Be sure that the hardware and software selected for backup are NDMP compliant. Spectra Logic hardware is NDMP compliant.