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Server backup support for drive pools larger than 2TB

    Question

  • Given that the VHD format doesn't support VHDs larger than ~2TB for dynamic or differencing VHDs (http://en.wikipedia.org/wiki/VHD_%28file_format%29#Limitations) and that this limitation affects Windows Server 2008 R2's server backup tool (http://social.technet.microsoft.com/Forums/en/windowsbackup/thread/35631672-e80d-4036-9e4d-e1878ed799c2), does Vail support server backups where the source drive pool is larger than 2TB?

    Has anyone tried this scenario yet?

    Related to larger storage pools, if the storage pool is larger than the server backup HDD, what does one do?  Is there provision for using multiple server backup HDDs (say backup database to one, other data to another)?  I know there's the ability to have two server backup HDDs and rotate them offsite, but I'm thinking here of 4 server backup HDDs (two on-site and two off).

    Thanks.
    • Edited by NigelMSB Saturday, May 01, 2010 8:52 AM Extra question added
    Saturday, May 01, 2010 7:51 AM

Answers

All replies

  • The server backup creates an VHD for each NTFS volume on the source. The drive pool size is not necessarily the issue. The limit is reached once any of the shared folders exceeds that capacity.

    There is also no way to create a server backup HDD pool currently.


    Bodhi Deb - MSFT
    Saturday, May 01, 2010 7:34 PM
  • The server backup creates an VHD for each NTFS volume on the source. The drive pool size is not necessarily the issue. The limit is reached once any of the shared folders exceeds that capacity.

    This will be fairly ugly for anyone that has ripped a lot of DVDs and/or BluRay disks to .iso images or TS_VIDEO. Which isn't me, but I know people who have 10 TB of videos all in a single share. This means that they will need to split that up into 5 shares (or more)...

    I'm not on the WHS team, I just post a lot. :)
    Saturday, May 01, 2010 9:14 PM
    Moderator
  • The server backup creates an VHD for each NTFS volume on the source. The drive pool size is not necessarily the issue. The limit is reached once any of the shared folders exceeds that capacity.

    There is also no way to create a server backup HDD pool currently.


    Bodhi Deb - MSFT

    Thanks for replying.  So that effectively limits Vail to 25 2TB volumes if they need to be backed up by server backup (50 TB is still a large number for today!).  That said, given that the largest HDD size right now is 2TB, the biggest limitation is the server backup destination drive size.  I wonder whether:

    - the two server backup destinatons exposed in the GUI could be used for 2 x 2TB (or whatever the largest HDD available is) sets of data (forgoing the one offsite/one onsite and just using offsite).

    or

    - one could use a custom scheduled task using WBAdmin to select data that would fit within 1 server backup HDD and use one task for backup HDD.

    or

    - use a USB enclosure that supports RAID 0 and exposes the concatenated size to the host OS.

    Luckily, I currently have 2 x 500GB and 2 x 1.5TB HDDs to backup, so 2 x 2 TB will do the trick for server backup (so I'm okay for now).

    The incrementals for Windows server backup are stored as shadow copies, so I wonder why server backup stores the VHD as a dynamic one.  The size should remain constant (with shadow copy incrementals) until the next full backup occurs and the VHD is replaced (which I think is up to 1 year for Windows Server 2008 R2/Windows 7 vs. 1 month for Vista, depending ). Perhaps when the oldest shadow copies are deleted, they are merged in to the VHD (http://blogs.technet.com/filecab/archive/2009/06/22/backup-version-and-space-management-in-windows-server-backup.aspx) rather than merged in with the next shadow copy (hence the need add/remove data from the VHD and hence a dynamic VHD).

     

    • Edited by NigelMSB Sunday, May 02, 2010 11:04 AM Added para. & typos
    Sunday, May 02, 2010 9:30 AM
  • You can always use wbadmin, or the powershell commandlets to do multiple policies as you described above. In the UI we limited it to 1 disk, to make things easier for normal users.

    Dont quite understand your VHD question. What's your concern? 

    -Bodhi


    Bodhi Deb - MSFT
    Sunday, May 02, 2010 7:07 PM
  • You can always use wbadmin, or the powershell commandlets to do multiple policies as you described above. In the UI we limited it to 1 disk, to make things easier for normal users.

    Great news - thanks.  Does using wbadmin/powershell affect the backup status reporting to the console?  That is, assuming that failed server backups generate alerts, how does Vail know which of the custom server backup tasks are required for a 'success' status?  Does one have to do without status reporting in this case?

    Dont quite understand your VHD question. What's your concern? 

    Sorry - I was rambling.  I was wondering why Windows Server 2008 R2 backup (which Vail backup is built upon) is limited to 2TB VHDs (given that fixed VHDs aren't limited).  I guess it uses a dyanamic or differencing VHD.  It is how it is, really - i was just curious as to which type is used and why it didn't use the fixed type.
    Sunday, May 02, 2010 9:45 PM
  • For status reporting I think it will pick up the first profile for reporting. In any case things are still being built in the server backup area, especially the status reporting (backup details in computers tab which is not in the current build). I will probably be able to give you a better answer during our next release cycle whenever that is. Feel free to file a suggestion bug through connect, and let us know your ideal scenario. Cant promise anything but if we do consider supporting multiple backup profiles we will at least go through the scneario while designing it.

    Not sure about the VHD type, my guess is it allows for the incremental backups. Let me follow up with the Windows team.

    thanks.

    -Bodhi


    Bodhi Deb - MSFT
    Monday, May 03, 2010 8:50 PM
  • drive extender volumes (aka shared folders) are backed using the File Based backup engine in windows server 2008 r2. volumes (c: and any regular NTFS volumes are backed up using the Block Based engine.  both engines exist in server 2008 R2 and the configuration on yoru vail server is automatic.

    All backups are incremental.  There is a slight difference in behavior between the FLB and BLB engines. FLB uses the USN journal to track changes where as BLB usese changed blocks.  BLB is more efficient but doesn't allow you to de-select a file or folder from the volume.  if you set up an NTFS volume for backup it will be configured for BLB, if you de-select a file then backup will automatically convert you to FLB.

    each folder gets it's own VHD and has a limit of 2TB.  folders can grow to larger than 2TB of course but i believe you found the real issue.  the practical limit of backup is going to be limited by the size of disks these days.  a separate, multi-disk drive enclosure that appears the system as a single USB drive will allow you to get past that

    You can, using WBADMIN, create separate a separate scheduled task to execute backup. Vail should monitor any of the failures that occur during a backup but there may be some missing information depending on how you use wbadmin and scheduled tasks. If you allow the backup wizard to create a policy and then add an additional sched task then vail will no longer ask you to configure a backup for example. 

    I am hoping for VHD 2.0 to have a higher max file size. 

    and i am also hoping for 20 TB USB drives that only cost $100. ;-)

     

     

     

    Wednesday, May 05, 2010 10:09 AM