Reported disk size of protected datasources larger than storage RRS feed

  • Question

  • Hello. I have a disk used as DPM storage, which has 13TB capacity. When I go to Management -> Disk Storage, highlight the disk, I can see the list of protected datasources located on this disk along with their sizes.

    However the total size of the datasources reported is almost 20TB. How is this possible? There's no deduplication.

    Tuesday, September 25, 2018 6:13 AM

All replies

  • Hello!

    Sound's strange, could you provide a screenshot of this? Also provide some information about your operating system and DPM version and build.

    Best regards,

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    Tuesday, September 25, 2018 1:28 PM

    There's the screenshot.

    DPM 2016 UR5, WS2016, LUN is formated as ReFS64k.

    Tuesday, September 25, 2018 2:15 PM
  • So you're using the new DPM Modern Backup Storage (MBS) feature which uses ReFs formatted volumes instead of disks.

    Note: The volumes cannot reside on a dynamic disk, make sure it is a basic disk.

    How did you create and add the volume to DPM?

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    Wednesday, September 26, 2018 9:56 PM
  • Yes, MBS. Since the GUI always uses ReFS4k, had to add it as folder to keep ReFS64k, so had to use Powershell:


    $dpmv = Get-DPMDiskStorage -Volumes -All | ?{$_.AccessPath -eq "$($DriveLetter):\"}
    Add-DPMDiskStorage -Volume $dpmv -Subdirectory 'DPM' -FriendlyName 'Backup'

    Thursday, September 27, 2018 6:12 AM
  • By folder do you mean a mount point?

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    Thursday, September 27, 2018 4:54 PM
  • No, by folder I mean a folder :)
    Thursday, September 27, 2018 4:56 PM
  • Hmm, what's your result when running the following command?

    Get-Volume  | Format-List AllocationUnitSize, FileSystemLabel

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    Thursday, September 27, 2018 5:14 PM
  • DriveLetter        : E
    AllocationUnitSize : 65536
    FileSystemLabel    : DPM-02

    As expected. What are you trying to get to?

    Thursday, September 27, 2018 5:19 PM
  • I asked because I haven't seen anyone doing it this way before, which makes me unsure whether this is supported or not.

    Either way it's possible be that DPM still thinks the disk is "4k formatted" but in reality it is 64k which makes the GUI show something completely off.

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    Thursday, September 27, 2018 5:29 PM
  • Well, not sure how 'officially' supported it is, but the cmdlet attribute to do it is there and I found this as a way to circumvent the DPM's ReFS4k fixed scenario, don't have the link to the source article anymore though.

    I'll calculate this for other disks used by DPM (which are also formatted ReFS64k) to see if it's also showing incorrect sizes, this particular one was easy to spot, since it holds the fewest protected objects.

    I'd hope DPM isn't so 'stupid' to have cluster size hardcoded for calculations like this :)

    Thursday, September 27, 2018 5:36 PM
  • I understand, let us know your calculations!

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    Thursday, September 27, 2018 6:37 PM
  • The calculation is off for every disk:

    DISK Capacity [GB] Unused space [GB] Protected data sources on this disk [GB] Difference [GB]
    E: 13311,81 1087,03 19276,12 -7051
    F: 15359,81 6438,67 9559,03 -638
    G: 15359,81 2126,9 14806,09824 -1573

    Difference = capacity - unused space - protected_data_size

    For disk G:, possibly data collocation might come into play since it contains SQL databases, but they're very small and it's also unlikely since E: and F: only contain VM host-level backups.

    Monday, October 1, 2018 8:33 AM
  • This is indeed strange with such a huge difference, have you tried just for testing purpose to create and add an NTFS disk to DPM and back up something to it to see if it also shows incorrect values?

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    Wednesday, October 3, 2018 10:44 PM