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Calculating size of incremental snapshots

Hello,

I'm currently in the process of reading through Azure documentation and while it appears that incremental snapshots fundamentally behave the same as on other platforms (Specifically GCP/AWS) I am having difficulty finding a way to get or calculate the size of incremental snapshots.

An explanation of incremental snapshots and the implementation specific to Azure I reference below is found here (https://azure.microsoft.com/en-us/blog/announcing-general-availability-of-incremental-snapshots-of-managed-disks/)

This first diagram in under 'Examples of incremental snapshots' shows that Snapshot-2 is only 20GiB, but references 100GiB from Snapshot-1. I'm specifically trying to find a way to identify Snapshot-1's size as 100GiB and Snapshot-2's size as 20GiB. Using the compute/snapshots/get api (https://docs.microsoft.com/en-us/rest/api/compute/snapshots/get) I am only given the 'diskSizeGB' which the snapshot was based on and is not representative of the cost of that specific snapshot for billing.

In the case of the second diagram it shows an example where Snapshot-1 was deleted and the size was rolled into Snapshot-2. In this case the goal would be to have Snapshot-2 show a size of 120GiB and Snapshot-3 to return a size of 5Gib.

Google's snapshot/compute api provides this value readily and with AWS it is possible to calculate via the EPS direct APIs for Snapshots with ListSnapshotBlocks and ListChangedBlocks between two existing snapshots. Is there something comparable within Azure?

Thank you,
Joseph

azure-virtual-machinesazure-virtual-machines-backupazure-virtual-machines-storage
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@JosephCWatts-7398 Thanks for raising this good question. I’m checking on this internally with the product team and will get back to you with something concrete. Apologies for the delay in responding here

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Sumarigo-MSFT avatar image
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Sumarigo-MSFT answered

@JosephCWatts-7398 I am sharing excerpt from the documentation to find the size used by incremental snapshots.

Azure Disk Storage overview - Azure Virtual Machines | Microsoft Docs
You can see the used size of your snapshots by looking at the Azure usage report. For example, if the used data size of a snapshot is 10 GiB, the daily usage report will show 10 GiB/(31 days) = 0.3226 as the consumed quantity.

Please let us know if you have any further queries. I’m happy to assist you further.


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JosephCWatts-7398 answered

@Sumarigo-MSFT
Thank you but this answer is slightly unfortunate as it does not entirely meet our needs... As a future hope for Azure would ideally be a value accessible via API for a large number of snapshots and not just a daily usage of data for an entire VM averaged over 28/30/31 days but the data at a more granular level of an individual snapshot.

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