Hello @Azur osm Welcome to Microsoft Q&A community forum!
Unless something has changed recently, Databox is a method for offline seeding and there is no concept of backing up to it long term. It can be used by the MARS agent and DPM/MABS but the intent is for large data-set seeding into a Recovery Services vault. So I’m confused by the ask about backing up VMs directly to Databox (and I assume you are looking for a solution for on-prem VMs?). You could protect on-prem VMs using DPM/MABS and then use the Databox for seeding to a vault, if that’s the intent.
For the second part of that regarding how much time for delivery back from Azure. These products (MARS/DPM/MABS) do not have an integrated restore process which ties in with Databox. Databox is a seeding-to-Azure process only wrt backups. We do have the Azure import/export service but the export is from Azure blob storage and I believe it would require some manual data copying to first restore data from the Recovery Services vault (to an Azure VM’s data disk most likely), then copy to Blob storage, then get the data out through the export service.
Hope this helps!
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