Hi Varma Thank you for reaching out to the Microsoft Q&A platform.
I'd be happy to help clarify your questions.
In Azure VMs, a data disk is an additional disk that can be attached to a virtual machine to store data and applications. When you create a VM, two disks are automatically attached to the virtual machine: an operating system disk and a temporary disk. Data disks are used for applications and data and can be added to the VM as needed.
The number of data disks needed for a VM depends on the workload and performance requirements. If the workload requires more storage capacity or higher IOPS, additional data disks can be added to the VM. So, we can say that data disks are increased when the workload requires more storage capacity or higher IOPS.
You can check the number of data disks attached to a VM in the Azure portal. To do this, go to the Virtual Machines page, select the VM you want to check, and then click on Disks under the Settings section. Here, you can see the number of data disks attached to the VM.
If you are working with custom images and the image mentions that the number of disks has increased during a certain operation, it means that additional data disks were added to the VM during that operation. This could be due to an increase in workload or performance requirements. It's important to note that the number of data disks needed for a VM can change over time, depending on the workload and performance requirements
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