Instance Size Flexibility

Microsoft announce the General Availability of Instance Size Flexibility for Azure Reserved Virtual Machine Instances. What does that mean in English?! Well, something quite interesting… Previously, when you purchased a Reserved Instance you had to choose the size of the VM (Standard_D8s_v3, for example) and the data centre (US West, for example). If you wanted to change those properties, then you needed to use the Exchange function to get a credit for the existing RI to use against a brand new RI with the required attributes. Now, however, it all works a bit differently.

You are no longer prepaying for base compute of a particular virtual machine type (Standard_D8s_v3), you’re prepaying for a certain amount of compute for a particular family – in this case, the DSv3 Series – in a specific data centre. Now, a Reserved Instance can be applied to any VM in that family, covering all or part of the base compute costs. If this sounds a bit mind-boggling then head to this page ( for a couple of examples of how it all works.

When you purchase a new RI with a Shared Subscription scope this option is your only optimisation choice, but if you choose a Single Subscription scope, then you can choose to opt for Capacity Priority instead, as shown in the picture below. This option can be changed later in the Configuration settings of the Reservation, if required.

Find the Microsoft announcement here:

Understanding Reserved Instance Pre-Payment

If you’re running full-time virtual machines in Azure then pre-paying for the compute power via an Azure Reserved Instance is a good way of saving money. The pre-paid amount is automatically applied to your running virtual machines and if you want to find out more about how this (apparently magic) process works, then this article is worth a read:

Azure Reserved VM Instances

Microsoft announce Azure Reserved VM Instances (RIs). There’s no word on launch date, but customers will be able to make big savings on Azure virtual machines by committing to 1 or 3 year terms for a particular VM type in a particular Azure region.

There will be flexibility for customers too with the ability to cancel the RI, or exchange it for another VM type in another data centre. Scott Guthrie’s blog post is here (see second to last paragraph):, and there’s useful information on too: