Windows Azure Geo Location Feature Terminology

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Here is some information about the terms and concepts introduced in the Dev Portal with the Windows Azure Geo Location feature.

The most important one is the notion of affinity group, which is now part of the creation wizard of the Windows Azure storage account and hosted services.

Affinity Group: An affinity group is a way of explicitly grouping Windows Azure hosted services and storage accounts in the same geo region. By putting them together in the same affinity group, you insure geographical proximity of the hosted services and storage accounts you place in the affinity group. Microsoft is abstracting the datacenter layer, hence the term “geo region” or “region”. The other attribute of an affinity group is its friendly name. You can change the friendly name of an affinity group at any time.

Geo Region / Region: This is the geographical area describing the location of the datacenter(s). With the first release of the Geo Location feature, there are three choices available:

  • USA – Southwest
  • USA – Northwest
  • USA – Anywhere

If you select “USA – Anywhere” you basically leave it to the software algorithm to pick where to deploy the hosted service or create the storage account.

It is important to note that the region cannot be changed.

Membership / Members: This is simply the list of hosted services and storage accounts –or members– within a given affinity group.

You cannot delete an affinity group if it contains any members. You first have to delete all members of an affinity group before you can delete the affinity group itself. Remember that you cannot delete a running hosted service, it has to be suspended first.

Unaffinitized: You may choose to leave a Windows Azure hosted service or storage account “unaffinitized”, which means that it is not related to other services or accounts you may have, or that it doesn’t matter whether they are in the same geo region or not.

Even if you leave a service or account unaffinitized you may still specify a geo region, depending on your needs for that service or account. Like for an affinity group, it is not possible to change the geo region of an unaffinitized service or account. It is set at creation time.