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When would a job with lower priority be granted resources before jobs with higher priority?

chucksysadmin
Level 2

Using Netbackup 7.5 with one master/media server, I have an NDMP job with a job priority set to 90 that's being granted tape resources before NDMP jobs I have set to a job priority of 95. Aside from priority, all of our NDMP policies are configured the same: 

- Full Backup

- Same retention level

- Same start window

- Same destination STU 

- Multiplexing level set to 1 

- Multistreaming is disabled

The storage unit is configured with 2 concurrent write jobs with multiplexing enabled and streams per drive set to 6. We have one robot with two drives. Why are lower priority jobs being granted resources before higher priority jobs? 

 

Thanks in advance for your help. 

 

Chuck

 

 

 

 

 

1 ACCEPTED SOLUTION

Accepted Solutions

Yasuhisa_Ishika
Level 6
Partner Accredited Certified

This happened at the beginning of start window? If so, "same start window" - so it is just because nbrb recieved request from lower priority job first. nbrb granted this request then recieved request from higher priority job.

If you need to ensure higher priority job run first, set the beginning of its start window earlier than that of lower priority jobs.

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3 REPLIES 3

Marianne
Moderator
Moderator
Partner    VIP    Accredited Certified

If queued job with lower priority can be written to same media that is already in a drive, this job will be submitted rather than a higher priority job that will need another tape to be mounted.

See http://www.symantec.com/docs/HOWTO86313

However, the following factors can cause a job with a lower priority to run before a job with a higher priority:

  • To maximize drive use, a low priority job may run first if it can use a drive that is currently loaded. A job with a higher priority that requires that the drive be unloaded would wait.

  • If a low priority job can join a multiplexed group, it may run first. The job with a higher priority may wait if it is not able to join the multiplexed group.

  • If the NetBackup Resource Broker (nbrb) receives a job request during an evaluation cycle, it does not consider the job until the next cycle, regardless of the job priority.

SymTerry
Level 6
Employee Accredited

As mentioned is this connect post, Resources that are already in use and available for lower priority jobs, will start in preference to high priority jobs if those resources are not available. 

The Symantec NetBackup 7.5 Administrator's Guide for Windows, Volume II talks about How NetBackup selects drives on page 131. 

Really it comes down to what the job is requiring and what is available. If 2 policies are identical and you give one a higher priority, and the resources are available, NetBackup will prefer the higher priority.

Yasuhisa_Ishika
Level 6
Partner Accredited Certified

This happened at the beginning of start window? If so, "same start window" - so it is just because nbrb recieved request from lower priority job first. nbrb granted this request then recieved request from higher priority job.

If you need to ensure higher priority job run first, set the beginning of its start window earlier than that of lower priority jobs.