Review of Preview – Azure Capacity Reservation

The long waiting feature is now Public Preview. When there is a Azure region disaster recovery, we need our VMs to be turned on in the secondary region. This feature guarantees you the recovery. You may learn about this feature in this URL

As you know already, Azure Site Recovery does not 100% guarantee to turn on your VMs in the event of DR. This feature addition helps you gaining more confidence with your BCP with this feature addition. 

  • Take a look at the Microsoft statement about the use cases for this feature. 
    • Business-critical applications—use on-demand capacity reservations to protect your capacity, for example when taking these VMs offline to perform updates.
    • Disaster recovery—you now have the option to set aside compute capacity to ensure a seamless recovery in the event of a natural disaster. The compute capacity can be repurposed to run other workloads whenever DR is not in effect. The VM maintenance can be handled by keeping core images up to date without the need to deploy or maintain VMs outside of DR testing.
    • Special events—claiming capacity ahead of time provides assurance that your business can handle the extra demand.

I have been asking for this feature for a long time now, and finally, it is here. I am happy about Microsoft as they are listening to customers and partners. However, the first bullet point is a bit worrisome as it states, It is not guaranteed to get your VM back if it is offline for some time due to maintenance. Does MSFT force customers to take this for all the critical workload? I hope they do not make things worse to this point. 

  • Key Points:
    • The cost of the VM capacity reservation is the same as your VMs. 
    • You can use your VM reservation for this as well. 
    • There is no commitment required, and you can use it as PAYGO. 
    • It permits the association of extra VMs beyond the reservation count of capacity reservation if there is availability, but you do not get the SLA benefit.  URL
    • You can assign a VM scale set to this. 
    • During the preview, you cannot avail of the SLA. 
    • During the preview, it is available for limited VM series only. 
    • You need to register for the feature using PS or CLI.
    • You can select your Capacity Reservation Group during the creation of your VMs on the advanced page.
    • Capacity reservation groups can be used for creating reservations for each VM size.
    • Only one VM size can be part of the one capacity reservation group.

When I tried configuring Capacity Reservation, I got the error. I need to check with Microsoft on this. It was showing as 0$ for the cost; maybe it is free during the preview as there isn’t an SLA commitment at this time. I have not seen a mention of mapping ASR-protected VMs to the capacity reservation group. Also, they should bring some flexibility with VM series than VM size with capacity reservation group. I wish Microsoft brings that option as well. In short, this is a welcome feature addition; in my opinion, let’s wait for the GA version.

You may also read my thoughts on changing the DR approaches with Public Cloud here.

Please send me your comments to help me improving the contents.


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