You can configure Commvault software to take consistent disk group snapshots for Oracle ASM. This applies only to Oracle ASM IntelliSnap backups using the Microsoft Azure snapshot engine.
Azure has introduced a new set of APIs to allow snapshots of multiple disks of a VM to be taken at the same time, for data consistency across all the disks. These snapshots are called VM restore points. For more information about VM restore points, see the Microsoft Azure documentation.
The previous Azure APIs for taking snapshots of disk resources did not allow multiple disks to be snapped at the same time. This approach was satisfactory for many popular volume managers and filesystems because the Commvault software coordinated the suspension of applications using the storage, before taking the snapshot. However, Oracle ASM has stricter requirements and stores additional metadata in its disk headers to ensure the consistency of its diskgroups. The serial nature of the previous Azure APIs for Azure snapshot creation created situations in which Oracle ASM may have been in the process of updating disk metadata between Azure snapshot API requests. This could have caused a header mismatch among the disks in a diskgroup. Snapshots of disks with inconsistent metadata cannot be mounted by ASM, which results in the loss of data. The new set of APIs solves this problem.
Commvault supports the new set of Azure APIs. You can enable the capability by setting the bEnableConsistentDiskGroupSnapshot additional setting. When you enable the additional setting, the system creates a VM restore point resource with consistent snapshots of the relevant disks. This is different from the traditional disk snapshot resource that is created in Azure.
The bEnableConsistentDiskGroupSnapshot additional setting is used for Oracle ASM IntelliSnap backups and only applies to the Azure snapshot engine. When the additional setting is set to true, the system takes consistent snapshots of all the relevant ASM disks at the same time. The snapshot engine performs a group snapshot of multiple disks.
Restrictions
You cannot use VM restore points across different Azure subscriptions. The snapshots contained in a VM restore point can only be used by a VM in the same subscription. If the destination VM is in a different resource group of the same subscription, it must have the Contributor Role for the resource group belonging to the VM restore point.
Best Practice
Keep disk names as short as possible. Azure disk snapshot names have a maximum length of 80 characters. Azure disk snapshots in a VM restore point will have an arbitrary unique string of considerable length appended to the original disk name. If the length of the concatenated disk snapshot name exceeds 80 characters, Azure API calls will fail.