Two Questions Regarding AWS' RDS Multi AZ

Question

1. I understand that when upgrading to a Multi-AZ rds from a Single-AZ, there occurs a \"breef i/o freeze\". What exactly does that mean?

2. When an upgrade i

Answer 1

the downtime when converting from single-AZ to multi-AZ is essentially the time it takes for a new instance to launch and become fully functional as sanket said, it may take a few mins.

scaling up a multi-AZ deployment first scales up the slave instance, then performs a failover. the downtime is the time it takes to do the actual failover - usually closer to a minute.

scaling out a multi-AZ deployment is done by adding additional read-replicas (sourced off of the standby) which incurs no interruption. keep in mind that adding read-replicas creates an eventually consistent system which may or may not be desirable.

it's also worth nothing that you should use the same instance types across all multi-AZ instances, otherwise the imbalance may incur replica lag.

as you're probably realizing, it's best to start with a multi-AZ configuration from the beginning. it makes scaling up and scaling out a lot easier and with less downtime.