Allow a reservation to be moved to a VM in a different AAD
I had setup a virtual machine and was testing over a period of a few weeks with a colleague. We needed to keep it up 24 hours a day and were pretty sure this machine was going to be in use for the long term, so I purchased a Reserved Instance to lower the cost.
As we continued our testing, it became obvious we needed to apply Azure Active Directory for increased security and management of users and groups. The VM was associated with the default AAD and after evaluating, I decided it should be in a separate AAD.
After creating the new Directory and re-creating the VM in the new AAD, I discovered the reservation could not cover the new, nearly identical, VM simply because it was in a different AAD. I had to cancel the reservation, get a refund, and purchase a new reservation, even though it was for essentially the same VM!
There must have been some good reason to restrict reservations by AAD but it seems rather silly that when using the same subscription and payment method, I can't keep a reservation to point to any matching VM under that subscription.
Jake Edwards commented
A simple "Change Directory" option on the Reservation (as exists with other resources/subscriptions) would resolve this and other issues (i.e. migration from PAYG to CSP).