Maximum concurrent jobs storage unit setting
The Maximum concurrent jobs storage unit setting specifies the maximum number of jobs that NetBackup can send to a disk storage unit at one time. The default setting is one job.
The maximum number of jobs that NetBackup can run concurrently is dependent on several factors and is not exclusively regulated by this setting. These factors include the following: the risk of reaching a disk full situation, the scheduling or capacity polling overhead, the media server I/O bandwidth, and various characteristics of the disk storage. No definitive method exists that can predict when a critical limit will be exceeded in a given system.
Note:
To specify a Maximum concurrent jobs setting of 0 disables the storage unit.
For example, three backup jobs are ready to be sent to the storage unit and Maximum concurrent jobs is set to two. The first two jobs start while the third job waits. If a job contains multiple copies, each copy applies toward the Maximum concurrent jobs count.
Note:
Increase the Maximum concurrent jobs setting if the storage unit is used for catalog backups as well as non-catalog backups. Increase the setting to ensure that the catalog backup can proceed while regular backup activity occurs. Where disk pools are used, increase the setting if more than one server is in the storage unit.
The Maximum concurrent jobs setting uses and dependencies are as follows:
Can be used to balance the load between disk storage units. A higher value (more concurrent jobs) means that the disk may be busier than if the value was set for fewer jobs.
The media server load balancing logic considers all storage units and all activity. A storage unit can indicate three media servers. If Maximum concurrent jobs is set to three and two of the media servers are busy or down, the third media server is assigned all three jobs.
This setting depends on the available disk space and the server's ability to run multiple backup processes. Where disk pools are used, the setting also depends on the number of media servers in the storage unit.
If multiple storage units reference the same disk pool, the number of concurrent jobs that can access the pool is the sum of the Maximum concurrent jobs settings on all of the disk storage units. The setting applies to the storage unit and not to the disk pool. Therefore, the job load is automatically spread across the media servers that the storage unit configuration indicates.
On Windows systems, even with multiple concurrent jobs, the time that is required for a job to complete depends on other factors:
The number of other jobs that are started at the same time.
The sequence in which the jobs were started.
The time that is required to complete each job.
See Impact when two disk storage units reference one disk pool.