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Offsite Tape backup strategy for DPM2010 RRS feed

  • Question

  • Greetings experts,

    I have been tasked with coming up with a backup strategy for offsite tapes. Unfortunately I am new to DPM. I have spent most of the morning reading some of the other posts in the DPM section and am not quite sure I fully understand how DPM actually works.

    DPM will be used for a D-D-T setup. We will be making Weekly(each Saturday) and Monthly(1st day of month) tape backups for Offsite storage.

    We have 6 PGs with around 8.3TB (currently) of data to back up.

    Colocation is active. We are using LTO4 tapes (800/1.6) and have a HP Storageworks 2024 Tape backup system (23 tapes and 1 cleaner).

    I am used to a system that just backs up until the tape is full and then continues on the next tape. You pull those, replace em, and move on.

    After reading the posts here though, I get the impression that this is not the way it happens with DPM and Colocation and even when the Weekly is done, I won't know which all tapes were used since they won't be marked ready for offsite until one of the Datasets is expired or the write-period ratio has been crossed.

    I read you can pull them without them being offsite ready but I don't want to have to search 23 tapes every Monday to see where it put everything. I also read that you cannot set a specific tape/s for a PG to back up to.

    Is there a common strategy that people use for offsite tape backup with colocation running??

    Or would it be easier to just put in the minimum amount of tapes (6 in this case - 1.6TB x 6tapes = 9.6TB of storage to cover my 8.3) and never have more than 6 tapes in the library so it is forced to fit all the data on those 6 tapes?

    Any help with this would be very much appreciated.

    Tuesday, January 17, 2012 8:25 PM

Answers

  • Hi,

    Actually, setting the WritePeriodRatio value to a "higher value" like 1 prevents the tape from being marked offsite ready until basically the 1st backup set expires.

    The only other setting that will prevent a new data set to be written to a tape is the TapeExpiryTolerance:

    Indicates the number of days over the furthest expiry date among all datasets on the tape that the tape will continue to be used.

    The default value is 17 percent.  Make that 100 decimal.

    This registry values is located under HKLM\Software\Microsoft\Microsoft Data Protection Server\1.0\Colocation.
                                          TapeExpiryTolerance:REG_DWORD:0x11

     

    Summary -  below settings will maximum time allowed to write to a tape in hopes of filling it up.

    Data Colocation Enabled

    TapeWritePeriodRatio: 1 

    ExpiryToleranceRange: 100 

    However, if you choose the above settings, be aware of this potential problem: http://social.technet.microsoft.com/Forums/en-US/dpmtapebackuprecovery/thread/0557249e-26e0-4e1d-8b83-59cb9e392649  for which we will be releasing a fix later in the year.

    FYI - These settings are more easily configurable in DPM 2012 and can be configured at the protection group level.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    • Marked as answer by JMahaf Thursday, February 16, 2012 6:36 PM
    Monday, January 30, 2012 9:38 PM
    Moderator

All replies

  • hi,

    Maybe changing the WritePeriodRatio will help you?

    WritePeriodRatio indicates the number of days for which data can be written on to a tape as a ratio of the retention period of the first data set written to the tape.

    WritePeriodRatio value can be between 0.0 to 1.0
    Default value is 0.15 (i.e. 15%)

    TapeWritePeriodRatio is not a registry. It is a global property for the DPM which needs to be set using DPM CLI command. Here is the command to set it

    Set-DPMGlobalProperty –DPMServerName <dpm server name> -TapeWritePeriodRatio <fraction>

    For example, if the retention period for the first data set written to a tape is 100 days, and you set the Write-Period ratio as 0.15, data will be written to the tape for 15 days from the day on which the first data set was written to the tape. After this period, the tape will be marked as offsite ready and no more data will be written to that tape until all recovery points have expired on that tape.

    Got this from another technet post: http://social.technet.microsoft.com/Forums/en-US/dpmtapebackuprecovery/thread/33f77a37-49ab-43d1-87d4-0b42b70beecf

     

    Hope this helps,



    Thursday, January 19, 2012 9:33 PM
  • Hi Jmahaf,

    <snip>
     I won't know which all tapes were used since they won't be marked ready for offsite until one of the Datasets is expired or the write-period ratio has been crossed.
    >snip<

    You missed one other condition that a tape will be marked offsite ready, and that is if the tape is full.

    Marthijin answer above is the correct answer to help fill the tapes.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Wednesday, January 25, 2012 2:20 AM
    Moderator
  • Although I don't really agree that the answer above was the answer I was looking for, I will let it be forced closed by the Moderator.

    "Marthijin answer above is the correct answer to help fill the tapes."

    Technically, it's not though. It will help the tapes go Offsite ready. It will do nothing to help the tapes fill up. At least, as I understand it.

    If there is an available tape, you cannot force DPM to share space on a tape.

    You can enable colocation so it "CAN" put it on one, but from everything I have read so far, you cannot force it to unless it has no other place to put it.

    Is this correct?

    Right now 7 tapes are marked as OS ready. These would hold a total of 11.2Tb but only 3 tapes are close to full. The other 4 have less than 700Mb each and every other tape in the drive has data written to it.

    I would really appreciate if you can show me a way to guarentee DPM will use the minimum number of tapes even if I have 23 empties in the tape drive.

    I don't really want to tell my CEO that we are going to spend an extra $50 per week in tapes because we chose DPM and you can't designate where the backups actually go to.

    Thanks


    • Edited by JMahaf Monday, January 30, 2012 9:17 PM
    Monday, January 30, 2012 8:26 PM
  • Hi,

    Actually, setting the WritePeriodRatio value to a "higher value" like 1 prevents the tape from being marked offsite ready until basically the 1st backup set expires.

    The only other setting that will prevent a new data set to be written to a tape is the TapeExpiryTolerance:

    Indicates the number of days over the furthest expiry date among all datasets on the tape that the tape will continue to be used.

    The default value is 17 percent.  Make that 100 decimal.

    This registry values is located under HKLM\Software\Microsoft\Microsoft Data Protection Server\1.0\Colocation.
                                          TapeExpiryTolerance:REG_DWORD:0x11

     

    Summary -  below settings will maximum time allowed to write to a tape in hopes of filling it up.

    Data Colocation Enabled

    TapeWritePeriodRatio: 1 

    ExpiryToleranceRange: 100 

    However, if you choose the above settings, be aware of this potential problem: http://social.technet.microsoft.com/Forums/en-US/dpmtapebackuprecovery/thread/0557249e-26e0-4e1d-8b83-59cb9e392649  for which we will be releasing a fix later in the year.

    FYI - These settings are more easily configurable in DPM 2012 and can be configured at the protection group level.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    • Marked as answer by JMahaf Thursday, February 16, 2012 6:36 PM
    Monday, January 30, 2012 9:38 PM
    Moderator