问题
When I restore a MySQL snapshot, I'm given the option to make the new instance Multi-AZ. However for some reason when I restore to Aurora, the "Multi-AZ Deployment" selection is disabled.
I thought possibly this meant it was automatically enabled. However when I go to the running instance details, it specifically lists Multi-AZ: "No".
Is there something I'm missing? Is there some other step I need to do to make Aurora Multi-AZ?
回答1:
Multi-AZ doesn't mean the same thing in Aurora as it does for MySQL and MariaDB. With Aurora, any replica in the cluster can take over for the master on failure (though the selection is based on priority, so it isn't just a randomly selected replica, if there is more than one replica), and the storage is already/always multi-AZ in Aurora because that's a core part of the Aurora design. So, Aurora can be "converted" to Multi-AZ.
Apparently, that's the only way it is done when creating an Aurora instance from a snapshot, based on this:
You can migrate a DB snapshot of an Amazon RDS MySQL DB instance to create an Aurora DB cluster.
...
You can migrate either a manual or automated DB snapshot. After the DB cluster is created, you can then create optional Aurora Replicas.
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Aurora.Migrate.RDSMySQL.html
If you create a multi-AZ Aurora cluster without a snapshot, that's all that happens -- a master and a replica are created. In that case, you can actually delete the replica and make it non-multi-AZ, which is a different process than what's involved with MySQL or MariaDB.
"Create a cluster" -- as used in the quote, above -- is a potentially confusing term, since you would naturally assume a cluster means two or more, but in fact an Aurora cluster can technically be a "cluster" of just one instance. Every Aurora instance is part of exactly one cluster. One instance is the primary (master) and any additional instances are replicas.
If the DB cluster doesn't contain any Aurora Replicas, then the primary instance is recreated during a failure event.
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Aurora.Managing.html#Aurora.Managing.FaultTolerance
来源：https://stackoverflow.com/questions/38928534/cant-create-multi-az-aurora-rds-instance