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DPM, Retention Period and expiry RRS feed

  • Question

  • Hi there,

    Here's the scenario.....

    We are using DPM 2010. We back up though the week to disk and to tape at a weekend. The retention policies we have in place are that weekly backups will be retained for 4 weeks and monthly backups (run on the last weekend of the month) are kept for 5 years - basically we don't want to ever re-use the monthly tapes and setting the protection to 5 years seemed a good way of doing it.

    For safeties sake we would like to take the tapes out of the drive by Tuesday each week at the latest.

    We have tape colocation enabled to make the most effective use of tapes.

    The trouble is this (as I understand it).....

    I need to set the TapeWritePeriodExpiry parameter ridiculously small (currently 0.001) if I am to have the monthly tapes set themselves to "Offsite Ready" within the time period I need. What this means though is that (for example), a tape that is written to on a Friday night may well then expire at some point over the weekend, maybe when it is only a quarter full - not exactly making the most efficient use of tapes. For our customers with smaller (8 slot) tape libraries this means that the library runs out of tapes before it has completed the backups.

    At the moment there are only 2 solutions I can see:

    1. On a Friday, set the parameter to be 1, so that data will just be written to the tapes constantly until they are full, then on a Monday set the parameter back to 0.001 so that all the tapes will immediately expire and will be present in the weekly DPM report that runs to identify the tapes to come out of the library. Obviously this introduces manual steps and will inevitably at some point go wrong!!
    2. Leave the parameter set at 1 and go back to the "old school" method of ignoring what DPM thinks should be in or out of the library and rotate tapes on a manual basis, labelling them as "Week1", "Week2", "Week3", "Week4", "January 2013", "February 2013".... etc. The Week1, Week2 etc. tapes would just get re-used each month at the appropriate week and as long as the retention period is set for 27 days it should work. But my worry is that this will confuse DPM no end and backups within the system will just get out of hand.

    The problem I believe is partly down to the parameter being global across all protection groups and retention periods.

    Has anybody any ideas on how best to approach the problem - I can't believe it hasn't cropped up before.

    Thanks

    John

    Friday, January 11, 2013 4:41 PM

Answers

  • Hi,

    I think you are overy concerned about the meaning of "offsite ready".  Nothing prevents you from removing a tape from the library before a tape is marked offsite ready.  It's just a visual cue that says "hey, this tape will not be used again until it's expired, so if you wish, remove it to make room for free tapes".  It sounds like you have a regiment in place that you replace tapes weekly be they full or not, so don't worry about the offsite ready flag, and stick to 2. it will not confuse dpm.

    FYI, if you want to be make sure no more than 1 weekly backup is on a set of tapes, you can adjust the TapeWritePeriodRatio to .20 - that will mean a weekly tape can only be written to for 20% of the retention range.  7x4 = 28 days retention.  20% of 28 = 5.6 days to finish the weekly backup, then the tape will be marked offsite ready. If you forget to change a tape, the next weeks backup will use a different free / expired tape, or fail if there are no tapes available.

    FYI - DPM 2012 allows you to adjust the TapeWritePeriodRatio and expiry tolerance at the protection group level, and gives you more granular control of which PG's get colocated.


    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.


    Friday, January 11, 2013 9:56 PM
    Moderator

All replies

  • Hi,

    I think you are overy concerned about the meaning of "offsite ready".  Nothing prevents you from removing a tape from the library before a tape is marked offsite ready.  It's just a visual cue that says "hey, this tape will not be used again until it's expired, so if you wish, remove it to make room for free tapes".  It sounds like you have a regiment in place that you replace tapes weekly be they full or not, so don't worry about the offsite ready flag, and stick to 2. it will not confuse dpm.

    FYI, if you want to be make sure no more than 1 weekly backup is on a set of tapes, you can adjust the TapeWritePeriodRatio to .20 - that will mean a weekly tape can only be written to for 20% of the retention range.  7x4 = 28 days retention.  20% of 28 = 5.6 days to finish the weekly backup, then the tape will be marked offsite ready. If you forget to change a tape, the next weeks backup will use a different free / expired tape, or fail if there are no tapes available.

    FYI - DPM 2012 allows you to adjust the TapeWritePeriodRatio and expiry tolerance at the protection group level, and gives you more granular control of which PG's get colocated.


    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.


    Friday, January 11, 2013 9:56 PM
    Moderator
  • Thanks for that reply Mike - that makes sense. One bit to clarify though - the only problems I see with setting the parameter to 0.2 are firstly that we would ideally remove the tapes by Tuesday and tale them offsite - sod's law would dictate that if there were to be a disaster at the site it would be early in the week when the tapes would then still be in the drive. However, and probably more importantly, since we want the monthly tapes to be retained for longer, the 0.2 of 5 years would be 1 year - which wouldn't therefore mark them as removable in the week! This also wouldn't be resolved in 2012 if the parameter is "global" for a protection group rather than be configurable per retention definition. Have I followed that correctly?

    Thanks

    John

    Monday, January 14, 2013 4:57 PM
  • Hi,

    Yes, that is correct, but most people want to use the tapes as long as possible - perhaps until they are filled, so that is what those settings control.  As stated earlier, nothing prevents you from removing tapes before they are full or marked off site ready.  So basically any tapes that have a monthly tape label on them can be removed from the library after the monthly backups complete.


    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.

    Monday, January 14, 2013 7:42 PM
    Moderator
  • Thank you for that - and your assistance. For the sake of being able to get tapes offsite, I think we will move to our own regime rather as discussed rather than using the inbuilt DPM control.

    Thanks

    John

    Tuesday, January 15, 2013 8:49 AM