We have SQL Sever setup on A-series virtual machines. We are wanting to upgrade to the D-series virtual machine. Is it as simple as just upgrading the VM in Azure and clicking save or are there any other things I need to watch out for? I have heard of people having issues upgrading due to the level not being available in the cluster that their Virtual Machines sit in.
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.
来源：https://stackoverflow.com/questions/27185330/upgrading-from-a-series-to-d-series-azure-virtual-machine