Forum Discussion

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 ha...
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 !

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.