none
How To Plan for Replicas vs Recovery Points? RRS feed

  • Question

  • According to my interpretation this article:

    https://technet.microsoft.com/en-US/library/hh758026.aspx

    I need to limit my data retention to 5 days in order to have a recovery point every 2 hours, however, the default configuration in 2012R2 is recovery points every 15 minutes and replicas 3 times a day. This leads me to believe that, for instance, I could actually have 364 days of retention if I had enough storage, as presumably each replica can have up to 64 recovery points (as opposed to there being a total of 64 recovery points possible).  I am assuming that the 64 recovery point limit is specific to VSS and each replica has its own set of VSS snapshots.

    While that is extreme, and not what I want to do, I would like a confirmation that I am understanding this or a more detailed explanation than I have already seen.  I have reviewed these three links and some other forum response (that I haven't found again to link here):
    https://technet.microsoft.com/en-us/library/cc161547.aspx
    https://technet.microsoft.com/en-us/library/cc161515.aspx
    https://technet.microsoft.com/en-us/library/bb809164.aspx

    However, the second article of the three linked above seems to imply that only 64 shadow copies can be kept and then the older ones are wiped.  Moreover, I'm not 100% certain those documents are for 2012 R2 since they go into shadow copies and have 2005 dates.  Given this ambiguity, rather than ask if I can have a specific configuration, I would like to have a few specific questions answered to help me understand this since the documentation isn't clearing things up for me:

    1) Before reviewing all of this to actually implement, I originally envisioned one replica ever, with unneeded delta/snapshot data being pruned and the replica being updated, so even one replica per day seems excessive to me.  Why would I want more than one replica per day?

    2) Does the answer to (1) change if I go from the default of recovery points every 15 minutes to recovery points every hour or two?

    3) I have shadow copies configured on a couple servers, and I would like to keep them in place.  Does the DPM client agent affect local shadow copies on file servers?


    Wednesday, August 12, 2015 3:33 PM

Answers

  • Hi,

    I think you have some terminology mixed up.

    Replica = a full copy of the protected data.  This is typically copied once at time of protection and is never created again.

    Recovery Point = A point in time that you can recover data from. A recover point for file server data is typically made once or twice a day.  Yes, there is a 64 recovery point limit for file server and client protection.

    For file protection (volume and shares and Client) there are two job types.

    A) synchronization = this brings over changed file data and applies them to the replica.  These synchronizations are not recoverable from recovery tab.  It controls how often you want to update the replica - the more frequent the synchronizations, the less risk of data loss should the protected volume or server fail.

    B) Recovery point - This is a VSS snapshot of the replica and represents a recovery point that you can recover data from.  No data is xfered when a recovery point is made. There is a 64 snapshot limit for file data.  You can make a manual recovery point without synchronization in between scheduled recovery points so you can recover data from the last successful synchronization.

    For protected volumes or shares, the time of the recovery point is the time you will see under the recovery tab.  Synchronizations for file data are not recovery points.  However, with that said, if you needed to recover a file between the last recovery point, and before the next recovery pointy is created, you can manually create a recovery point and recover files from that intermediate recovery point assuming one or more synchronizations were successful in between.   

    So, if you are doing synchs every 2 hours, and the last RP was at 7:00AM, and at 2:00pm the protected server power supply goes belly up, the last synch was at 1:00pm, so you could manually make a recovery point without synchronization, and that restore point would include file changes up to and including 1:00PM synch, so in essences you only lost 1 hr worth of changes before the server became inaccessible. The longer time between synchronizations, the more changes you miss bringing over to the DPM server and potentially lose should the protected server croak.

    For file protection Windows support 64 snapshots per volume, so based on your retention period, you could take more recovery points per day and have more recovery point times to choose from each day.   IE: 1 RP / day = 64 days max protection.   6 RP / day = ~ 10.5 days max protection.

    Q3) I have shadow copies configured on a couple servers, and I would like to keep them in place.  Does the DPM client agent affect local shadow copies on file servers?

    A3) No, you can keep local shadow copies on the protected server and they will not be effected by DPM. However, end user recovery from DPM recovery points will not be possible if you maintain local shadow copies on the protected server.

    Hope this helps you.


    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, August 21, 2015 2:55 AM
    Moderator

All replies

  • Hi,

    I think you have some terminology mixed up.

    Replica = a full copy of the protected data.  This is typically copied once at time of protection and is never created again.

    Recovery Point = A point in time that you can recover data from. A recover point for file server data is typically made once or twice a day.  Yes, there is a 64 recovery point limit for file server and client protection.

    For file protection (volume and shares and Client) there are two job types.

    A) synchronization = this brings over changed file data and applies them to the replica.  These synchronizations are not recoverable from recovery tab.  It controls how often you want to update the replica - the more frequent the synchronizations, the less risk of data loss should the protected volume or server fail.

    B) Recovery point - This is a VSS snapshot of the replica and represents a recovery point that you can recover data from.  No data is xfered when a recovery point is made. There is a 64 snapshot limit for file data.  You can make a manual recovery point without synchronization in between scheduled recovery points so you can recover data from the last successful synchronization.

    For protected volumes or shares, the time of the recovery point is the time you will see under the recovery tab.  Synchronizations for file data are not recovery points.  However, with that said, if you needed to recover a file between the last recovery point, and before the next recovery pointy is created, you can manually create a recovery point and recover files from that intermediate recovery point assuming one or more synchronizations were successful in between.   

    So, if you are doing synchs every 2 hours, and the last RP was at 7:00AM, and at 2:00pm the protected server power supply goes belly up, the last synch was at 1:00pm, so you could manually make a recovery point without synchronization, and that restore point would include file changes up to and including 1:00PM synch, so in essences you only lost 1 hr worth of changes before the server became inaccessible. The longer time between synchronizations, the more changes you miss bringing over to the DPM server and potentially lose should the protected server croak.

    For file protection Windows support 64 snapshots per volume, so based on your retention period, you could take more recovery points per day and have more recovery point times to choose from each day.   IE: 1 RP / day = 64 days max protection.   6 RP / day = ~ 10.5 days max protection.

    Q3) I have shadow copies configured on a couple servers, and I would like to keep them in place.  Does the DPM client agent affect local shadow copies on file servers?

    A3) No, you can keep local shadow copies on the protected server and they will not be effected by DPM. However, end user recovery from DPM recovery points will not be possible if you maintain local shadow copies on the protected server.

    Hope this helps you.


    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, August 21, 2015 2:55 AM
    Moderator
  • Thank you, very helpful.  I think the confusion stemmed from a protection group I had created that was protecting both files and application data.  Separating protection groups between files and different applications made things a lot clearer.  I thought the synchronizations were to reduce data transferred at a given time, but great point about being able to create a recovery point if needed.
    Friday, August 21, 2015 12:01 PM