Azure VM SLA if we use mixed disk SKUs ( Premium for OS & data , Standard HDD for backup)

Question

Would like to know what would be impact on VM SLA if we use mixed disk SKUs.
Is it going to be composite SLA?

Scenario --> Azure VM with all premium SSDs for OS and data drives and for backup purposes we are using standard HDD.

• For any Single Instance Virtual Machine using Premium SSD, Ultra Disk or Premium SSD v2 for all Operating System Disks and Data Disks, we guarantee you will have Virtual Machine Connectivity of at least 99.9%.

https://azure.microsoft.com/en-in/support/legal/sla/virtual-machines/v1_9/

Answer 1

Hello, @Sajan S S !

What is my VM SLA if I mix disk types?

When determining composite SLAs, you're looking at multiple components that represent possible points of failure. If you rely on a VM and a database for example, and your application wouldn't run if either were to go down then the composite SLA would be based on those two services.

From the details provided in your scenario, it sounds like you have a 99.9% SLA for your single instance VM using Premium SSDs and in addition to the single instance VM using Premium SSD, you have an HDD backup.

There is only a composite SLA if your application requires both the single instance VM using Premium SSDs and the HDD backups in order to run. It sounds like you only need the single instance VM using Premium SSD if all is going well which provides a 99.9% SLA. In addition, you have HDD backups for anything that would require an HDD backup within the 0.1% that is outside the SLA (more than routine maintenance or that sort of thing).

I hope this has been helpful!