question

Hello @GazJones-5919,

Thank you for reaching out to the Microsoft Q&A platform. Happy to answer your question.

Answering the specific questions:

The issue is that the resource group itself doesn't have a "global" location... it has to be placed in a specific region.
Yes, thats correct, resource group needs to be placed in a specific location irrespective of the location of its resources, it can be placed anywhere.

From my understanding, if you have a resource in region X but place the resource in a resource group which is region Y, then if region Y fails, the resource will continue to function, but you will be unable to update the resource (add/ remove/ modify) until region Y comes back online.
For example say your resource is a VM which is Y and your Resource Group(RG) is X, if region of VM(Y) goes down only Y is not accessible while RG(X) is still functional for use, you can manage it for creating/modifying/deleting other resources in that RG(X)
RG is just a logical container to group resources together.

For the sceanrio:

A scenario:
We have a resource group:
Resource Group: rg-backuptest-weu-001 (location: WestEurope)

In this resource group, 2 resources:
Resource: rsv-vmbak-weu-001 (location: WestEurope)
Resource: rsv-vmbak-eus-001 (location: EastUS)

If West Europe goes down (unavailable due to outage). My question:
- Does resource 'rsv-vmbak-eus-001' continue to backup VM's for the East US region during the outage of West Europe?
Yes, the EastUS Vault will continue to backup as it doesn't have any impact on the vault or its storage. Also in case of a region down scenario, the RGs will be still accessible only the resources like compute, storage, network will be impacted. As RG is not a resource in azure datacenters.

• Can you restore backups from 'rsv-vmbak-eus-001' to the VM's for the East US region during the outage of West Europe?
  Yes, you can restore the VM back to its original location or an alternation location in the same region as source VMs.

• What limitations affect the resource 'rsv-vmbak-eus-001' in the East US region during the outage of West Europe?
  Nothing will be impacted. These 2 regions are totally different and doesn't have any dependency here. Even though the RG is is WE, you can still access your vault and perform restores.

Please "Accept as Answer" and Upvote if the answer provided is useful, so that you can help others in the community looking for remediation for similar issues.