Question: I've been looking into securing videos, and one thing I've run into is the concept of encrypting the output of a video source file. This happens after the user is authenticated and access granted (for example RTMPE is one of the instances of such encryption). What I don't get is why this serves any useful point at all for DRM purposes - and I'm not talking about RTMPE in specific, I just mean encryption of any sort at all from a server to client perspective.

After all, if I am granted access to the video, and now I'm playing it and setting it to whatever the maximum resolution is, assuming different resolutions are behind different paywalls, I could just open up OBS, record my desktop at 5000 kbps, and get an amazing rip - and encryption would do absolutely nothing to hinder me, because I'm totally bypassing the fact that I can't easily download it directly. 

So my question is, why bother with encryption on videos? It wouldn't prevent automated video farming as long as proper user credentials are presented either I think? And furthermore, there's a sort of downside in that all the encryption technologies as far as I can find available for web usage has compatibility with one device class or another, such as RTMPE not working on iOS, which is pretty well used. I presume there would also be more battery life issues, as I tend to run out of battery much faster when playing Flash videos rather than HTML5. So, why not just authenticate and stream it straight up over, say, html5 without any encryption?

Answer: 
The hardware infrastructure used for A series VM is not suitable for D series VM. It might be possible that the cluster where the VM is hosted, has the hardware configuration required for creating A series VM alone.

However if you would still want to change from A series to D series VM, you will have to export disks and create a new VM using the previously saved disks.

Going forward as a workaround: when you create your very first VM in your Cloud Service, be sure to specify one of the D-SERIES size even if you do not need it immediately. Doing this, your Cloud Service will be “tied” to a cluster that will support both A-SERIES (except A8/A9) and D-SERIES, then for all the future VMs contained in the same Cloud Service. Now, you can create additional A-SERIES VMs and mix together in the same Cloud Service. If you do not need the first D-SERIES VM, you can now safely delete it.
If the D-series machines are not available due to the cluster, you can always delete the vm (preserve the disks) and create a new VM of the D-series and attach the existing disks to that system.
When you create the new VM, choose the option to 'create from template' and the select your OS disk from the 'My Disks' section. Then attach all the data disks to the VM once it's provisioned.