Veritas NetBackup™ Administrator's Guide, Volume I

NBRB evaluates the requests sequentially and sorts them based on the following criteria:

• The request's first priority.

• The request's second priority.

• The birth time (when the Resource Broker receives the request).

The following scenarios present situations in which a request with a lower priority may receive resources before a request with a higher priority:

• A higher priority job needs to unload the media in a drive because the retention level (or the media pool) of the loaded media is not what the job requires. A lower priority job can use the media that is already loaded in the drive. To maximize drive utilization, the Resource Broker gives the loaded media and drive pair to the job with the lower priority.

• A higher priority job is not eligible to join an existing multiplexing group but a lower priority job is eligible to join the multiplexing group. To continue spinning the drive at the maximum rate, the lower priority job joins the multiplexing group and runs.

• The Resource Broker receives resource requests for jobs and places the requests in a queue before processing them. New resource requests are sorted and evaluated every 5 minutes. Some external events (a new resource request or a resource release, for example) can also trigger an evaluation. If the Resource Broker receives a request of any priority while it processes requests in an evaluation cycle, the request is not evaluated until the next evaluation cycle starts.