Availability Set and Availablity Zone SLA difference

Question

I have migrated onpremises application to Azure Cloud now.

I missed to create Availability set for set of virtual machines.

And created VMs in different Availability zones. My superior is seeking if the SLA is 99.95 atleast ?

Which one is provides better availability ? AV-zone or AV-Set ?

Do I have to create AV-set and then recreate the VMs under it ? to achieve High availability ?

Answer 1

Hi @Pratik Deenbandhu
Thank you for posting in Q & A forum.

An availability set is a logical grouping of VMs that allows Azure to understand how your application is built to provide for redundancy and availability. We recommended that two or more VMs are created within an availability set to provide for a highly available application and to meet the 99.95% Azure SLA. There is no cost for the Availability Set itself, you only pay for each VM instance that you create.
VMs must be created within the availability set to make sure they are correctly distributed across the hardware. An existing VM cannot be added to an availability set after it is created.
https://learn.microsoft.com/en-us/azure/virtual-machines/availability-set-overview

An Availability Zone is a high-availability offering that protects your applications and data from datacenter failures. Availability Zones are unique physical locations within an Azure region. Zone-redundant services replicate your applications and data across Availability Zones to protect from single-points-of-failure. With Availability Zones, Azure offers industry best 99.99% VM uptime SLA.
https://learn.microsoft.com/en-us/azure/availability-zones/az-overview?context=/azure/virtual-machines/context/context

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