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newbie_girl's avatar
newbie_girl
Level 3
16 years ago

maximum concurrent write drive

 

Below is page 231 of the 6.5 NetBackup AdminGuide1 UnixServer. If I am understanding the paragraph that I bolded italicized in red font below, in a case of the where the master/media server has 2 attached tape drives, but the STU is set to a max concurrent write drive to 1…. (assuming that NBU does not specify which drive to use for backup and which to use for non-backup tasks, just that it can only use 1 drive for backups)

  • If a drive is down and the other drive is still up…

  • backups will still fail because the still up drive is only "available for restores and other  non-backup operations"

Maximum concurrent write drives

The Maximum concurrent write drives setting specifies the number of tape drives that NetBackup can use at one time for jobs to this storage unit. The number of tape drives available is limited to the maximum number of tape drives in the storage device. If a job contains multiple copies, each copy applies toward the Maximum concurrent write drives count.

 

Select one number for a:

■            storage unit that contains only stand-alone tape drives. Specify a number that is less than or equal to the number of tape drives that are in the storage unit.

■            robot. Specify a number that is less than or equal to the number of tape drives that attach to the NetBackup media server for the storage unit.

 

Assume you have two stand-alone drives of the same density and specify 1. Both tape drives are available to NetBackup but only one drive can be used for backups. The other tape drive is available for restores and other non-backup operations. (For example, to import, to verify, and to duplicate backups.)

 

I am looking for Symantec expert to confirm or deny my understanding of the manual.   I have asked 4 people (3 people who do NBU work, and 1 person who doesn’t even know what NBU is) and only 2 agree with how I comprehend the paragraph.  Thank you in advance!

 

 

 

 

 

7.1.x and Earlier
Backup and Recovery
Configuring
NetBackup
  • Karthikeyan_Sun's avatar
    Karthikeyan_Sun
    16 years ago

     Newbie_Girl:

    • If a drive is down and the other drive is still up…
    • backups will still fail because the still up drive is only "available for restores and other  non-backup operations"

     

    you are wrong ! Say you are having 2 Drives with the state(1-up,1-down), then if backup start first(assuming you didnt use priority); and it will utilize any one drive and other can be used for any restore or duplication or other non backup operation.

    backup wont fail!

    in other hand, say you are getting 2 restore jobs and retsore can utilize that 2 drives, and backup jobs that are coming after restore should wait for the restore to complete !

    I think you got my point !

    Let me know if you have any more clarifications !

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  • stu1's avatar
    stu1
    Level 4
    16 years ago

    Think of that as a user-definable limit. 

    If you had 2 tape drives available for jobs. Setting max job per drive does not mean you have no drives for restore.  It means, now backups can use up both drives.  If a restore is requested, it has to wait until 1 drive is available (when all backups are completed).

    Users have requested that they can set a limit to how many drives out of the total to use for backups. If the user has 2 drives, they can limit 1 for backups at any given time; but never both.  1 would then always be availeble for non-backup jobs such as restores.

    Today, the common practice is to set this value to equal all the drives, so you have all drives available for backups.  As usually you would be performing backups more often than restores; it's usually not ecomonical to commit 50% of your tape drive capacity to restores; unless your specific shop requires it.

    It's more command when users have robotic libraires of 10 or more drives to perhaps set the limit to 9 or so, so most drives are doing backups, and they have atleast 1 drive available for other things. 

    Keep in mind again, that it doesnt mean restore is limited to 1.  Restore will use any drive that is available including up to the total drives regardless of limits, as long as they are next in the queue and of higher priority.

  • Karthikeyan_Sun's avatar
    Karthikeyan_Sun
    Level 6
    16 years ago

     Newbie_Girl:

    • If a drive is down and the other drive is still up…
    • backups will still fail because the still up drive is only "available for restores and other  non-backup operations"

     

    you are wrong ! Say you are having 2 Drives with the state(1-up,1-down), then if backup start first(assuming you didnt use priority); and it will utilize any one drive and other can be used for any restore or duplication or other non backup operation.

    backup wont fail!

    in other hand, say you are getting 2 restore jobs and retsore can utilize that 2 drives, and backup jobs that are coming after restore should wait for the restore to complete !

    I think you got my point !

    Let me know if you have any more clarifications !