Using Azure Affinity Group Removes Virtual Network

Question

I'm new to Azure and am working on some basics that I can't find any consistent information on at the Microsoft Azure site.

My understanding is that the use of Affinity Groups makes sure your virtual resources are very close to each other. So I created an affinity group for West-US. Then I created a cloud service which I'm going to use for my AD controllers. I assigned my affinity group to it. When I created my VM and selected my ad cloud service, I could not select the local network I had created. I could only place a VM in my local network only if a region was assigned during the creation of a cloud service as opposed to using an affinity group.

Can someone please shed some light on the practical use of when and where I create affinity groups, if at all?

Thank you.

Answer 1

Affinity groups were historically a way to ensure proximity between Azure compute and Azure Storage. Until about three months ago a VNET also had to be created in an affinity group. One of the problems with this is that an affinity group is tied to physical hardware in a datacenter so that when new hardware came along (such as high-memory SKUs) a cloud service or VNET hosted in an existing affinity group could not get access to it. This led to some frustration.

Any VNET created now should be a regional VNET NOT an affinity-group VNET - i.e., one hosted in a region not an affinity group. In fact, you can only do the former in the Azure portal. I suspect that much of the motivation for using an affinity group disappeared when Azure migrated to a flat high-speed network a couple of years ago.

I recently blogged a more extended discussion of affinity groups.