Microsoft's current practice of Pooling Reserved Instances by VM Type has it's merits, since it ensures that a Reserved Instance will be 'used' whenever possible, but Microsoft should also provide for the capability of linking a specific VM to a Reserved Instance.

We have a situation where we have more VMs of a particular configuration type (e.g. B4ms) than the number of Reserved Instances that we have purchased. The goal of purchasing the Reserved Instances was to exclude the compute costs of specific VMs for the 3-year period and be able to bill-back the hourly compute costs of the remaining non-Reserved Instance VMs to our internal users. But since all the B4ms type VMs can occupy the Reserved Instances, we cannot get the accountability that we need because the VMs occupying the Reserved Instances change everytime one is power-cycled for maintenance or a patch.

Simply: It would be great if I could check a box in the properties of a specific VM to indicate whether it should or should not participate in the Reserved Instance Pool!
Regards