Queries related Managed disks snapshot

Question

Hi Team,

We have few questions related Disk Snapshots, Please can anyone answers my query as soon as possible.

What is Benefits of Disk snapshot ?
What could be disk's snapshot size generally if my disk size is 256GB ? we also have 25TB of disks running currently. what could be snapshot size of 25 TB disk then ?
What cloud be Restoration time for snapshot from blob storage. For 25 TB of SSD disk how much time required?
If frequency of snapshot is on weekly basis, then new snapshot will be override with old one and new copy will be created ? how this done basically?
If data is less than disk size then how snapshot price is calculated ? will it take full disk snapshot or only data will be taken as snapshot ?
What is the default retention period of disk snapshot? or how long period snapshot can be remained in blob storage?
How daily and weekly snapshot pricing can be calculated , as from azure calculator we cant see pricing to calculate snapshot weekly basis ?
if we want 15 min snapshot to be taken then how will be pricing ?

Answer 1

@Jayesh Sawant Many of these are answered by our documentation here: https://learn.microsoft.com/en-us/azure/virtual-machines/disks-incremental-snapshots
Also refer to the Disk Pricing page for questions on cost: https://azure.microsoft.com/en-us/pricing/details/managed-disks/

• A managed disk snapshot is a read-only crash-consistent full copy of a managed disk that is stored as a standard managed disk by default. With snapshots, you can back up your managed disks at any point in time. These snapshots exist independent of the source disk and can be used to create new managed disks.

Snapshots are billed based on the used size. For example, if you create a snapshot of a managed disk with provisioned capacity of 64 GiB and actual used data size of 10 GiB, that snapshot is billed only for the used data size of 10 GiB. 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.

• Restore disk Restores a VM disk, which can then be used to create a new VM.
  Azure Backup provides a template to help you customize and create a VM.
  The restore job generates a template that you can download and use to specify custom VM settings, and create a VM.
  The disks are copied to the Resource Group you specify.
  Alternatively, you can attach the disk to an existing VM, or create a new VM using PowerShell.
  This option is useful if you want to customize the VM, add configuration settings that weren't there at the time of backup, or add settings that must be configured using the template or PowerShell.
• You can store full snapshots and images for Premium SSDs on Standard storage. You can choose between locally redundant (LRS) and zone redundant (ZRS) snapshot options. These snapshots and images are charged at €0.046/GB per month for both Standard LRS and ZRS options based on the used portion of the disk. For example, if you create a snapshot of a managed disk with provisioned capacity of 64 GB and actual used data size of 10 GB, snapshot will be billed only for the used data size of 10 GB. If you choose to store them on Premium SSDs Managed Disk storage, you will be charged at €0.108084/GB per month.

You can store incremental snapshots for Premium SSDs only on Standard storage. They are charged at €0.046/GB per month for both Standard LRS and ZRS snapshot options of the storage occupied by the delta changes since the last snapshot. For example, you are using a managed disk with provisioned size of 128 GB and used size of 100 GB. The first incremental snapshot is billed only for the used size of 100 GB. 20 GB of data is added on the disk before you created the second snapshot. Now, the second incremental snapshot is billed for only 20 GB.

• Azure Disk Backup offers multiple backups per day. If you require more frequent backups, choose the Hourly backup frequency with the ability to take backups with intervals of every 4, 6, 8 or 12 hours. The backups are scheduled based on the Time interval selected. For example, if you select Every 4 hours, then the backups are taken at approximately in the interval of every 4 hours so the backups are distributed equally across the day. If a once a day backup is sufficient, then choose the Daily backup frequency. In the daily backup frequency, you can specify the time of the day when your backups are taken. It's important to note that the time of the day indicates the backup start time and not the time when the backup completes. The time required for completing the backup operation is dependent on various factors including size of the disk, and churn rate between consecutive backups. However, Azure Disk backup is an agentless backup that uses incremental snapshots, which doesn't impact the production application performance.

Duration depends which tier have you chosen: https://learn.microsoft.com/en-us/azure/storage/blobs/lifecycle-management-overview
A blob can have any number of snapshots. Snapshots persist until they are explicitly deleted, either independently or as part of a Delete Blob operation for the base blob. You can enumerate the snapshots associated with the base blob to track your current snapshots.

When you create a snapshot of a blob, the blob's system properties are copied to the snapshot with the same values. The base blob's metadata is also copied to the snapshot, unless you specify separate metadata for the snapshot when you create it. After you create a snapshot, you can read, copy, or delete it, but you cannot modify it.

Any leases associated with the base blob do not affect the snapshot. You cannot acquire a lease on a snapshot.

You can create a snapshot of a blob in the Hot or Cool tier. Snapshots on blobs in the Archive tier are not supported.

A VHD file is used to store the current information and status for a VM disk. You can detach a disk from within the VM or shut down the VM, and then take a snapshot of its VHD file. You can use that snapshot file later to retrieve the VHD file at that point in time and recreate the VM.

• Job status showing summary of backup and restore operations and their status in the last seven days. Back up Azure Managed Disks
  Incremental snapshots are billed for the used size only. Incremental snapshots will always use standard HDDs storage, irrespective of the storage type of the disk
  Also make sure to read out the restrictions of incremental snap shots https://learn.microsoft.com/en-us/azure/virtual-machines/disks-incremental-snapshots?tabs=azure-portal#restrictions
• You can generate a read-only shared access signature (SAS) URI for the managed disk and use it to copy the contents to a private storage account or on-premises storage. You can use the SAS URI using the Azure portal, Azure PowerShell, the Azure CLI, or AzCopy
• You can take a snapshot of their managed disks and then use the snapshot to create another managed disk.

Source: Azure Docs FAQ

Introducing cost-effective increment snapshots of Azure managed disks

• You can take a snapshot of their managed disks and then use the snapshot to create another managed disk.

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

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