How NetBackup selects drives
NetBackup stores media information and device configuration and status information in the EMM database. When a robotic mount request is issued, the NetBackup Resource Broker (nbrb) queries the EMM database for the media ID of the volume requested. If the volume is in the EMM database, the media request is matched with a compatible drive in the robot. The mount request is forwarded to the appropriate robotic daemon (UNIX) or process (Windows) based on the location of the media. Location is the robotic library and the storage slot number, if applicable.
A drive must meet the following criteria to be selected for the mount request:
The drive is configured.
The drive is in the robotic library that contains the media.
The drive allows the requested media density.
The EMM service (nbemm) manages the drives and requests for locally-attached or shared drives in the EMM domain.
The EMM service manages the drives by doing the following actions:
Determines which of the drives are currently available.
A drive is available if it is one of the following:
Configured as UP
Not assigned
Compatible with the media type
Not reserved by another host
Picks an available drive that was least recently used.
NetBackup selects the robotic-based drives over standalone drives unless the correct media already is loaded in a standalone drive.
The first drive in the drive configuration is used first, and then the second drive, and then the next. Use the tpconfig -d command to see the drive order in the configuration.
If some of the drives are shared drives, NetBackup chooses a nonshared drive first (if one is available). NetBackup chooses a shared drive first so the shared drives can be used on other hosts that share the drives. Shared drives require the Shared Storage Option.