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Maximum number of tape libraries DPM 2012 can read from simultanously? RRS feed

  • Question

  • Hello,

    I've been asked a question while delivering DPM 2012 training and can't find an answer. The question is how many separate tape drives can DPM 2012 read/write from simultaneously?

    Thanks in advance,

    Marcus

    Tuesday, August 13, 2013 3:37 PM

Answers

  • Hi,

    OK - I just remembered that the DPM task scheduler only allows 50 active tape backup jobs - so in essence the accurate answer to your question would be 50 simultaneous tape backups running across 50 tape drives. 


    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.

    Tuesday, August 13, 2013 5:31 PM
    Moderator

All replies

  • Hi,

    There really is not a limit, each protection group (PG) allows you to select a tape library for tape backups. If the library chosen has multiple tape drives inside, you can specify how many you want DPM to use simultaneously to perform the backups of the protected data sources in that PG. This means backups could be spread across multiple tapes as multiple backup jobs will be writing to multiple drives.   If you select only a single drive, all backups will be written to one tape at a time.

    If you had lets say 5 protection groups, you can specify the same library but only select one drive allocated in each PG. That way all five PG's can backup at the same time, each to a separate drive.

    If you have only standalone tape drives not in a medium changer or library, then you would need to select different drives in separate protection groups if you wanted DPM to use all of them.


    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.

    Tuesday, August 13, 2013 5:06 PM
    Moderator
  • Hi Mike,

    Thanks for the reply, I think the question was more around is there a supported limit? We've been going through the various tape library functionality using a VTL.

    My reply was it would depend on server specification etc... what's the higher number of drives you have known be used?

    Many thanks,

    Marcus

    Tuesday, August 13, 2013 5:11 PM
  • Hi,

    I'm not aware of and have not heard of any problems associated with the number of tape drives.  We have seen DPM console MMC crashes associated with a high number (over 1500) SLOTS in a library.

    Should you ever experience that issue, you can just modify the below value to be 4E20 and that will usually fix that issue.

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows
      USERPostMessageLimit:REG_DWORD:4e20


    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.

    Tuesday, August 13, 2013 5:21 PM
    Moderator
  • Thanks. May have a come back one I've spoken to the guy who asked! Many thanks.

    (I'm also just starting a new thread about SharePoint backup you may be able to help with!)
    Tuesday, August 13, 2013 5:26 PM
  • Hi,

    OK - I just remembered that the DPM task scheduler only allows 50 active tape backup jobs - so in essence the accurate answer to your question would be 50 simultaneous tape backups running across 50 tape drives. 


    Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.

    Tuesday, August 13, 2013 5:31 PM
    Moderator
  • That's great. So in a DR situation if they could get 50 tapes into the right places they could theoretically run 50 simultaneous restores?! I can't see this happening in reality, but I have an answer now, so many thanks!

    Tuesday, August 13, 2013 5:34 PM