none
Possible to span one large protection group over multiple stand-alone tape drives (or simply over multiple tapes?) RRS feed

  • Question

  • Hello all,

    We have a fairly simplistic DPM setup. We have various protection groups protecting our servers' data and one stand-alone tape drive onto which our long-term backups are stored.

    Recently our largest protection group seems to have become too large to fit on one tape. We figured this was a good time to upgrade our tape deck to a two-drive one we have lying around.

    We now have Dell PowerVault 114T with two Ultrium 3 drives. These both show up as stand-alone drives in DPM (from what I read, this is expected as this isn't a "library".

    Is there a way to have DPM span a protection group over multiple tapes, preferably over both tape drives for concurrent/automatic spanning? I have been reading through threads and the closest I can find is that you need a library to achieve this and there seems to be no (documented) way to force multiple stand-alone drives into a library.

    All I can think of is to daisy chain the drives to the same SCSI channel but I don't know if this would be helpful at all. . .

    Monday, October 10, 2011 1:17 AM

Answers

  • Your only options are:

    A) Live with having to change tapes when the large PG is backed up.

    During a tape backup if a tape becomes full and there are no other tapes marked free, Free (contains data) or expired in the library, DPM will raise an alert to prompt for another free tape to continue backup. It will wait for 1 hour by default before failing the job.

     

    This prompting timeout can be configured by the registry entry “PromptingTimeOut” under “HKLM\Software\Microsoft\Microsoft Data Protection Manager\1.0\Prompting”

    PromptingTimeOut:REG_Dword:43200000  (dec) = 12hrs


    The Formula is   (#hrs * 1000 * 60 * 60)

    1HR =  1*1000*60*60 =  3600000  decimal


    So for each hour to wait, multiply by 3600000.

    8hrs = 28800000  decimal

    B) Use a real tape library that will change tapes for you automatically.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Saturday, October 29, 2011 4:10 PM
    Moderator

All replies

  • Hi AMS,

    The best way to use tape management with DPM is to use a library. DPM will manage the writing and "spanning" itself, you cant alter this by your self they way you want.

    So, if your tape gets full DPM will need another tape inserted to continue write the data onto. One thing you could do is to allocate also the second tape drive in the protection group when you modify the protection group (look at Select Library and Tape Details), this would possible help you a little bit further but it will not solve your problem.

    The solution for you is to use either a VTL (Virtual Tape Drive) like Firestreamer or buy a tape library so DPM can manage the tapes by itself. 


    Best Regards

    Robert Hedblom

    MVP DPM


    Check out my DPM blog @ http://robertanddpm.blogspot.com

    Monday, October 10, 2011 8:38 AM
    Moderator
  • Hello Robert,

    I attempted to allocate the second tape drive in the protection group but it doesn't seem to let me as it only allows the selection of one library (where one stand-alone drive is seen as a library). I can't change "Drives allocated" from "1" either.

    Sigh, It seems like I might have to break up the protection group into two smaller ones to get them backing up.

    Monday, October 10, 2011 11:09 PM
  • Hi AMS,

    If you choose to break up the protection group into two smaller ones you should still be able to choose tape drive A for one protection group and tape drive B for the other protection group.

    This meens that you should in theory be able to run the tape backup jobs at the same time, this reduces your backup window


    Best Regards

    Robert Hedblom

    MVP DPM


    Check out my DPM blog @ http://robertanddpm.blogspot.com

    Tuesday, October 11, 2011 8:28 PM
    Moderator
  • I was going to try that but the protection group is made up of several subfolders all within the same drive on a file server. DPM doesn't seem to allow you to create multiple protection groups from the same drive. . .
    Tuesday, October 11, 2011 10:49 PM
  • Your only options are:

    A) Live with having to change tapes when the large PG is backed up.

    During a tape backup if a tape becomes full and there are no other tapes marked free, Free (contains data) or expired in the library, DPM will raise an alert to prompt for another free tape to continue backup. It will wait for 1 hour by default before failing the job.

     

    This prompting timeout can be configured by the registry entry “PromptingTimeOut” under “HKLM\Software\Microsoft\Microsoft Data Protection Manager\1.0\Prompting”

    PromptingTimeOut:REG_Dword:43200000  (dec) = 12hrs


    The Formula is   (#hrs * 1000 * 60 * 60)

    1HR =  1*1000*60*60 =  3600000  decimal


    So for each hour to wait, multiply by 3600000.

    8hrs = 28800000  decimal

    B) Use a real tape library that will change tapes for you automatically.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Saturday, October 29, 2011 4:10 PM
    Moderator