DPM 2016 Modern Backup Storage ReFS Volume offline and in RAW state

A couple of weeks ago a customer reported problems with a DPM 2016 server with Modern Backup Storage (MBS). Modern Backup Storage is a new approach of DPM to get a more efficient and flexible storage pool without the known limitations of the LDM database. With MBS you use storage spaces on the DPM server to add the disks to a large pool. Then on top of the storage space you create a volume or several with shares that the DPM server can use as storage instead of adding unallocated disks that DPM manages.

An explanation on MBS is not part of the scope of this blog but the problem that we had with it is related to Storage Spaces and more specific to ReFS volumes. ReFS is the new file system Microsoft has been cooking on for the last 6+ years. It has many improvements and several of them are used to make sure data corruption does not occur and if it occurs it repairs it automatically or takes actions to prevent it.

So why seems the volume on this DPM server offline, inaccessible and corrupt in a RAW file format?

In this setup

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DPM 2016 Modern Backup Storage and Deduplication performance issue

Modern Backup Storage and Deduplication

One of the great features of Hyper-V in combination with a virtual DPM server was the ability to use deduplication. On the Hyper-V host you have a volume which is enabled for dedup where you place your .vhdx files on that serves as backup storage for the virtual DPM server. This way you can safe a lot of disk space.

Since DPM 2016 you can use Modern Backup Storage (MBS). With MBS you can use Storage Spaces to create a volume with shares that you present to DPM. Now I hear you thinking hey, we can enable Dedup on that volume and let DPM backup data to that volume and it get’s deduped so we can use a physical machine to… Unfortunately not, because MBS requires ReFS as file system on the disk, Dedup is ruled out because it is not yet supported and not available on ReFS volumes.

So we still need a physical Hyper-V host with an NTFS volume for the .vhdx files with dedup enabled. In the VM we create the storage space with a virtual disk and a ReFS volume and you are ready to cruise with your DPM server.

The setup

So the situation above also discribes the setup a bit. In short we have a physical host that has storage for the virtual DPM server. In this case it was a disk enclosure attached to the host with several SATA disks that we added to a storage space. On top of the storage space a mirrored volume was created to place the backup .vhdx files on. The host takes care of the deduplication of the backup data inside the .VHDX files. The vm takes care of the Storage Space and DPM.

The physical host has to take care of some dedub jobs like optimizing, garbage collection and scrubbing. These jobs cost a big amount of IO and a large amount of

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