Microsoft Announces Preview of On-Demand Capacity Reservations for Azure Virtual Machines

Recently, Microsoft announced the preview of capacity reservations on request for Azure Virtual Machines (VMs). This new feature for VMs allows customers to reserve more compute capacity.

Previously, customers could only get a service level agreement (SLA) for Azure Virtual Machines capacity when deploying actually active or stopped VMs. This operation can create management overhead to keep all VMs up to date and hinder the use of compute for other business purposes. Customers can now deploy and manage the compute capacity needed to run Azure VMs separately from the VMs themselves with the on-demand capacity reservation feature.

In an Azure virtual machine blog post, Bill DeForeest, chief program manager at Microsoft, explains how the on-demand capacity reservation feature works:

An on-demand capacity reservation works like a deployable object: specify a VM size, location, and quantity using the Compute Resource Provider. After successful completion of a reservation, customers can then allocate VMs to the reserved capacity. The reservation is on-demand as no term commitment is required. You can delete capacity reservations on demand when they are no longer needed.

In addition, a blog post by means of Alan Kinane, Azure technical lead at MicroWarehouse, outlines a key benefit of the position:

I’ve often wondered what would happen if an entire Azure region went down and there was a capacity struggle in the paired region when customers call their DR plans. Is there enough capacity for everyone? This is where on-demand capacity reservations come in. Once this feature becomes generally available, you can expect a service SLA (yet to be published) that describes what Microsoft is willing to guarantee in terms of resource availability.

Another benefit for customers is the ability to pre-claim capacity when additional demand is expected.

Because no commitment is required, Microsoft places a pay-as-you model for reservations – meaning that the reservation price depends on the underlying costs of the VM size, location and quantity of the reservation. Also note that, according to the same blog post, any discounts will be applied to customers who have purchased Reserved Instance (RI) VMs.


The on-demand capacity reservation preview is currently available for common Azure VM families, Burstable (B), Av2, Dv2, and later generations including Dav4, memory-optimized Ev3 and later generations, including Eav4 and compute-optimized (Fv1 and newer) . In addition, the company plans to support additional VM series soon.

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