April 22, 2022 at 8:16 am
Why do we use Always On?
It is because we want to have high availability and disaster recovery.
In case our production SQL Server is down, Always On will switch the production server to secondary instance.
However, after migrated to Azure, we don't need to have the above concern, rights?
So we can migrate our on-premise Always On servers to Azure as a just stand alone database.
Am I correct?
April 22, 2022 at 2:45 pm
No far from it.
Even in Azure you need to think about your HADR options and that’s both at IaaS and PaaS offerings.
While Azure SQL Database (PaaS) will move around the region, what if the region is dead, where is your DR.
VMs do not move between zones in the region, so you need multiple VMs to give HADR even in region. The machine usually has to be reallocated in the second zones which actually causes downtime.
There should be plenty of documents on zonal vs zone redundant infrastructure deployment methods on the web so for what can fail between zones and cannot depending on multiple factors.
Remember the cloud is just someone else’s computer, while somethings are different 99% of what you need to do in the cloud still remains.
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