Estimating costs - Azure Backup

Info paraphrased from official documentation..

The size of the backed-up data determines the pricing for Azure Backup in each protected instance before compression and encryption -
* For virtual machines, the size of the allocated disk determines the data size.
* When backing up files and folders, the size of the files and folders configured for backup determine the data size.
* When backing up SQL Server, the size of the databases configured for backup determine the data size.

The new pricing model for Azure Backup has two components:
* Protected instances: This is the primary billing unit for Azure Backup. Customers pay for the number of instances that are protected with the Azure backup service. The price per protected instance depends on the categorisation of the instance in the pricing table
Size of each instance Azure Backup price per month
Instance < or = 50 GB $5 + storage consumed
Instance is > 50 but < or = 500 GB $10 + storage consumed
Instance > 500 GB $10 for each 500 GB increment + storage consumed

* Storage: Customers can choose between Locally Redundant Storage (LRS) or Geo-Redundant Storage (GRS) for their backup vault. The net price for Storage depends on the amount of data stored with the service. The backup data in each vault will be billed at the appropriate LRS or GRS Block Blob rates for the region where the vault is located.

Usage is pro-rated based on the number of days in a month that an instance has been protected.

For as long as your data is retained with Azure Backup, you will continue to pay for both Protected Instances and Storage. Your Protected Instances bill is based on the size from the last successful backup before you decided to stop protection. Your Storage bill is based on the total amount of data stored in the backup vault for that instance.

What is not charged:
* Customers will not be charged for any restore operations or outbound network bandwidth (egress) that is associated with restore operations.
* You do not have to pay for storage transactions with Azure Backup. These are included as part of the software price that you pay.

Examples - 

Backup of a 100 GB virtual machine:
The Protected Instance charge is $10 per month. Every day, 1 GB of data is added and the data is retained for 120 days, and you are charged for the storage for that separately. After 1 month, if you decide to stop protection of the virtual machine but retain the data in Azure Backup, then you will be charged $10 per month until the backup data is explicitly deleted by you.

For protecting the 250 GB of SQL Server databases to Azure Backup, the SQL Server is treated as a protected instance. As the size of the protected instance is greater than 50 GB but less than 500 GB, the price is $10 per month. If the virtual machine is also backed up to Azure Backup, it is counted as another protected instance. As the virtual machine size is between 50 GB and 500 GB, its price is also $10 per month. Virtual machine backup and in-guest workload backup are charged independently.

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