On-Demand Capacity Reservations for Azure Virtual Machines (Public Preview)
What is On-Demand Capacity Reservation in Azure?
On-Demand Capacity Reservation gives you the ability to reserve compute capacity in a specified Region or Availability Zone in Azure, to ensure you have the VM sizes you require available to you when you need them.
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How do I create an On-Demand Capacity Reservation?
When creating an On-Demand Capacity Reservation you specify the following three properties:
·???????VM Size –Select which VM size you would like for your reservation (e.g. D8s_v3)
·???????Location – Select your Region, or Availability Zone, (if this is available in the Region selected).
·???????Quantity – Select the number of instances you wish to reserve within that location
Once you have created and deployed the Capacity Reservation, the capacity is available straight away and reserved for your use only. To allocate a VM to the Capacity Reservation, you must specify the reservation as one of the VM’s properties. If this is not done, then the reservation will remain unused.
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How is the On-Demand Capacity Reservation charged?
When you deploy a Capacity Reservation, you are charged for the entire Capacity Reservation, whether you have provisioned a VM in the reserved slots or not. These are charged at standard PAYG prices for the entire reservation, even if the reservation is not being used
Example:
You create a Capacity Reservation for 10 D8s_v3 VMs and deploy 6 D8s_v3 VMs within this Capacity Reservation. Your Azure bill will show 6 D8s_v3 VMs and 4 unused Capacity Reservation slots. Both the used and unused capacity will be charged at PAYG prices* for the underlying VMs size.
*Assuming a Reserved Instance has not been applied (Please see below)
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How does this differ to Reserved Instances?
Reserved Instances offer a discount on compute prices, in return for a 1- or 3-year commitment, whilst an On-Demand Capacity reservation offers you a guaranteed capacity in a set location.
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Can I apply reserved Instance Pricing to an On-Demand Capacity Reservation?
Yes, you can. Reserved Instances can be applied to both used and unused capacity within a Capacity Reservation to combine the benefits of both offers.
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Can I change/cancel On-Demand Capacity Reservations?
Of course, flexibility is built into the offer to allow you to respond to demand.
Capacity Reservations are not set to any commitment terms. You can deploy and delete these at any time without a term commitment, giving you flexibility when you need it.
If you are looking to change the reservation capacity, then this can be done at any time (assuming there is additional capacity in the required location/zone). However, VM Size and Location/Zone can not be changed. To alter this, you would need to delete the current Capacity reservation and deploy a new one with the required VM Size and Location/Zone specifications.
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What is the use case for On-Demand Capacity Reservations?
Capacity Reservations ensure you have access to the VM size you need, where you need it, without any concerns about availability not matching your requirements. This could be a requirement for larger VM sizes required for critical workloads or the number of VMs required to ensure scalability for you applications.
Typical scenarios for using Capacity Reservations would include the following:
·???????Scalability for mission-critical application
·???????Business Continuity
·???????Disaster Recovery
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Other FAQs
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What happens if the capacity is not available when creating the reservation? – If the location selected does not have sufficient capacity to meet the request, then the Capacity Reservation will fail to deploy. You must then select another VM size and/or region/zone.
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Which VM sizes can be allocated? - Only Av2, B, D, E, & F VM series are supported during public preview.
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What is the SLA for VMs under a Capacity Reservation? - Capacity Reservations will come with Azure availability SLA for use with virtual machines. However, the SLA won't be enforced during Public Preview and will be defined when Capacity Reservation is in General Availability