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Daily/Weekly/Monthly backups using a tape library RRS feed

  • Question

  • Hi,

    I am trying to setup Grandfather-Father-Son tape backups using DPM2010 with a tape library, but have come across various questions which has prevented me from doing this and I have been unable to find the answer to.

    1. How does DPM decide what tape to write to next in the tape library?
    2. Is there any way to ensure given 4 tapes are left in the library, DPM will always write to the same daily tape each week (i.e. the Monday tape is always written to on Mondays and Tuesday Tape is always written to on Tuesdays etc.). Would placing them in particular slots help ensure this? Ideally, I would like to label the daily tapes Tues-Fri, but if the above is not possible there seems little little point in labelling them.
    3. How long does DPM retain the catalogue for a tape? Does it get deleted automatically when the end of the retention period is reached, or when the tape is next over-written?
    4. If I add a "weekly" tape to the library on Monday for the first time, what can I do to ensure that DPM doesn't backup to it before Saturday? Or is my only realistic option to add the Saturday tape on the Friday? I know that by adding on Friday it would work because it would be the only tape which is free or has expired. But for practical reasons I would like to do this on Monday i.e. just after removing the last Saturday tape to take off-site.
    5. What if a daily tape doesn't quite expire before the next week's backup is due to start? Can this happen? If I want to be 100% sure that the tape (e.g. Tuesday backup tape) expires before the next backup is due start (on the Tuesday the following week), would setting the long-term retention period to 6 days (rather than a week) be a good way to address this?

    Configuration:

    • Short-term: D2D each night. Retention 2 weeks. No co-location.
    • Long-term: D2T each day Tues-Sat. Co-location enabled.
    • Tape Library: LTO5 autoloader (8 slots)
    • All PGs (which have a long-term goal set) fit onto one tape (with co-location) and all tapes have a bar-code.

    Many Thanks,

    Bruce.










    • Edited by Redbruce Tuesday, February 28, 2012 10:25 PM
    Tuesday, February 28, 2012 9:19 PM

Answers

  • Hi,

    Q1. How does DPM decide what tape to write to next in the tape library?

    A1. DPM has a flat tape management model. DPM will use tapes as needed based on a few factors like TapeWritePeriodRatio and TapeExpiryTolerance settings, Co-location setting and recovery goals.   See this post for details on these settings: http://social.technet.microsoft.com/Forums/en-US/dpmtapebackuprecovery/thread/298da32d-5660-4e0e-b38a-378108eaa9e4

    Q2. Is there any way to ensure given 4 tapes are left in the library, DPM will always write to the same daily tape each week (i.e. the Monday tape is always written to on Mondays and Tuesday Tape is always written to on Tuesdays etc.). Would placing them in particular slots help ensure this? Ideally, I would like to label the daily tapes Tues-Fri, but if the above is not possible there seems little little point in labelling them.

    A2.  No, DPM does not reserve tapes for certain days of the week.  DPM uses tapes based on recovery goals (retention period) and the above mentioned settings. Using external labels is not a good way to keep track of tapes when using a tape library.   I would just rely on barcodes as DPM will show what tape(s) are required when restoring data. The tape management report will tell you when a tape is expired and due back so it can be reused.

    Q3. How long does DPM retain the catalogue for a tape? Does it get deleted automatically when the end of the retention period is reached, or when the tape is next over-written?  

    A3. By default, the catalog is pruned when the protection group retention range expires, but is configurable if you want it pruned sooner.

    Q4. If I add a "weekly" tape to the library on Monday for the first time, what can I do to ensure that DPM doesn't backup to it before Saturday? Or is my only realistic option to add the Saturday tape on the Friday? I know that by adding on Friday it would work because it would be the only tape which is free or has expired. But for practical reasons I would like to do this on Monday i.e. just after removing the last Saturday tape to take off-site.

    A4.  DPM has limited options on how long a tape is written to and are based on A1 above.  We have better options in DPM 2012.  For DPM 2010, Unless the TapeWritePeriodRatio or TapeExpiryTolerance is exceeded, or the tape gets full, DPM should continue writing to the same tape and should not grab a free tape until it needs it.

    Q5. What if a daily tape doesn't quite expire before thet next week's backup is due to start? Can this happen? If I want to be 100% sure that the tape (e.g. Tuesday backup tape) expires before the next backup is due start (on the Tuesday the following week), would setting the long-term retention period to 6 days (rather than a week) be a good way to address this?

    A5.  DPM does not have the option to select days for retention period for tape based backups, the minimum is 1 week. Assuming a 1 week retention, we're currently working on a fix to ensure that Tape-X written to on DAY-Y can be reused on DAY-Y the following week.  The fix is currently being tested and should be included in the next roll-up fix later this year. In the meantime, add an additional tape to your rotation.


    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.


    Wednesday, February 29, 2012 12:54 AM