All About Azure Reservation – Disks

We talked about Azure Reservation for VM in my previous blog post. If you have not read it already, I suggest you to read it.

The VM RI discounts applicable only to the VM infrastructure cost but it does not include disks or storage used. Azure Disk Storage reservations combined with Azure reserved VM instances help you reduce total VM cost.

The common rules are applicable here as well “Use it or Lose it”,

Currently, Azure Disk Storage reservations are available only for selected Azure premium SSD SKUs. But it doesn’t apply to unmanaged, ultra disks and page blob consumption.

disk reservation

The reservation for disk is not based on capacity but it is based on total number of disks per SKU. That means you make reservation consumption based on the units of the disk SKUs instead of the provided size. Example, you cannot use P40 reservation for 2 P30 disks. It is does not have instance flexibility like in VM reservations.

Validate below mentioned points before you purchase disk reservation. (Updated on 12th April 2020).

  • It is applying to the disks SKUs only but not for snapshots which will be charged as PAYGO.
  • It is applying to the managed disk resources hourly basis.
  • When you delete a resource, the reservation discount automatically applies to another matching resource in the specified scope.
  • Unused hours don’t carry forward.
  • It can be applied up to one year, 3 year reservation is not available today.
  • Track the usage in disk SKUs instead of disk capacity.
  • Unmanaged disks or page blobs cannot be reserved today.
  • Standard SSDs or Standard HDDs cannot be reserved today.
  • All other Premium SKUs smaller than P30 cannot be reserved today.
  • Disks in Azure Gov, Germany and China region cannot buy disk reservation today.

It supports tiering the capacity. Suppose, you want to use a total of 200 P30 premium SSDs for 2 hours. Also suppose you use only 100 for the first 60 minutes. During this period, your use is fully covered because you made a reservation for 100 P30 disks. If you then discontinue the use of the first 100 (so that you’re using zero) and then begin to use the other 100 for the remaining 60 minutes, that usage is also covered under your reservation.

All common rules around cancellation, exchange and refund of reservations are applicable for the disks as well.

  • No limits on the number of exchanges you can make.
  • No fee applicable with an exchange.
  • You can change a reservation property such as family, series, version, SKU, region, quantity, and term with an exchange.
  • The new reservation that you purchase must be equal or greater value than prorated credit from the original reservation.
  • The new reservation purchased as part of exchange has a new term starting from the time of exchange.
  • You can cancel reservation any time and you will get prorated refund based on the remaining term. But there will be 12% early termination fee applicable.
  • When it expires, the disk in the scope will be applied with PAYGO rate.
  • You will get an email notification 30 days prior to the expiry.

If you are using lot of premium disks for your VMs, you may consider to use disk reservation along with your VM reserved instances.

You may read my blog post on Azure Storage reservation here.

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