Discovery:  How much space is needed for a backup? Does the backup partition have to be bigger than the uncompressed backup size?

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    PRODUCT:

    BMC Discovery


    COMPONENT:

    BMC Discovery 11.3


    APPLIES TO:

    BMC Discovery



    QUESTION:

    How much space is needed for a backup? 
    Does the backup partition have to be bigger than the uncompressed backup size?
    What is the backup compression ratio in practice?


    ANSWER:

    To see approximately how much space will be required for a Discovery backup, do the following:

    From the UI, go to Administration > Backup&Restore

    This page shows how much space the uncompressed backup would take. Divide this by two to get the maximum size of the backup (it will almost certainly be smaller).

    In the case of a local backup, the new backup will replace the existing one. Therefore, ignore the free/used space of the local backup partition. Just take into account the full size of the partition to check if it is big enough.

    Example:

    User-added image

    So, for this particular backup in the screenshot, Discovery would need 376.6 gb / 2 = 188.3 gb available for a backup.

    The full size of the local backup partition should be larger than that number.  If the backup is close to the partition size, consider using the "Reduce backup size" option, or move the backup to a larger disk.

    Please note that compacting the datastore on a regular basis will reduce the backup size, and can also improve performance.

    The guidance is that the actual backup size could be 50% of the uncompressed backup size. However, that ratio is typically better in practice. Here are some test results with Discovery 11.3.05:
    - an estimated size of "788.8 MiB (uncompressed)" generated a 155mb backup (compression ratio = 20%)
    - an estimated size of "340.8 MiB (uncompressed)" generated a 95mb backup (compression ratio = 27%)

    Here are some additional tests run on a Discovery 11.3.0.6 cluster. The first test was run with a two member cluster. A third member was added for the second test.

     
      Two Members: 
                                                                                                                                 
    Projected Backup Size278.3 MB
    Projected Backup Size276 MB
    Actual Backup size88.1 MB
    Actual Backup size86.6 MB
    Total:174 MB (compression ratio = 31%)
       
      Three Members: 
                                                                                                                                                                             
    Projected Backup Size278.3 MB
    Projected Backup Size275.8 MB
    Projected Backup Size278.3 MB
    Actual Backup Size65.8 MB
    Actual Backup Size80 MB
    Actual Backup Size77.8 MB
    Total:223 MB (compression ratio = 27%)
       
    Note: These tests were performed with the    "Reduce Backup Size" option. This option removes the Datastore Index files from the backup. Using this option should not impact the overall compression ratio, but will make the backup smaller than it would be without that option selected. It's noted in the UI that this will result in a slower restore. This is because the indexes will be re-built during restoration. 

     


    Article Number:

    000249317


    Article Type:

    FAQ/Procedural



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