Aurora Multi-AZ versus reader instances - paid instances and available zones?
We are moving from mysql to aurora on a production environment, so having multi-az/high availability is required. At this moment a replica cluster is begin setup - see screenshot.
My question is about multi-az, "high availability" and the reader instances (not storage)
During creation, multi-az was selected. The expectation was to see 1 reader instance marked as multi-az - but we ended up with 2 reader instances.
So I am confused, do we now have 2 instances that are both multi-az (as in, 4 paid instances in total) or does the interface points out that the cluster contains 2 readers (2 paid instances in total) which are considered as multi-az? (as stated in the multi-az columns as "2 zones", meaning eu-west-1c and eu-west-1b - adding another reader in zone -1a will then display 3 zones?)
Next to that, the terms "high availability" in combination with multi-az are throwing me off...
Thanks for any details!
-- Rob
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Once it is created in a multi-az, you will have one reader and one writer as shown below
When you create one additional reader on top of it then it will be like below
However when you create a replica and select multi-az on the regional cluster it will have a replica cluster with one writer and one reader and if you do no multi-az then it will have a replica cluster with writer as shown once created. Then in case fail over you can move application from current primary to the cross-region replica by promoting your cross-region replica to be the new primary from the Amazon RDS console.
when using multi-az and once it is done creating
when using no multi-az and once it is done creating
You have an RDS MySQL instance that is replicating to an RDS Aurora Cluster. The cluster has two reader nodes. When you promote that cluster one of the reader nodes will flip to a writer node.
"When you promote that cluster one of the reader nodes will flip to a writer node." Super clear - that is indeed the case after the cluster was done setting up.
Thanks
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Nice, that clears up the "Multi-AZ" colum with "x zones". So all instances, writer or reader, are counted into the nr of zones, acting as "Multi-AZ".
Thanks!