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RDS Switch From Multi-AZ to Single-Zone

This article demonstrates how to downgrade an RDS MySQL instance from multi-availability-zone (Multi-AZ) to a single instance (single zone). The process is simple and worked well in my test. If I was to do this in a production environment, I would a) dump the database first just in-case the process failed, and b) make sure there was sufficient time allocated to the outage (change management) to import the database into a new instance if all goes bad.

While creating the test environment in AWS, I used the following settings:

  • MySQL 5.6.40
  • DB T2 Micro
  • Selected: Create replica in different zone
  • Selected: Provisioned IOPS (SSD)
  • Selected: 100GB
  • ap-southeast-2a

I was able to log in and see the databases hosted in the RDS service:

$ mysql -h testrds.lksjdfkdsjf.ap-southeast-2.rds.amazonaws.com -u admin -p
Enter password: 
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 16
Server version: 5.6.40 Source distribution

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MySQL [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| innodb             |
| mysql              |
| performance_schema |
| sys                |
| testdb             |
+--------------------+
6 rows in set (0.00 sec)

MySQL [(none)]>

While logged into the AWS web portal, I had to wait 10 minutes for the “Modify” button to become active for the test RDS instance. Once active, I changed the setting “Multi-AZ deployment” from “Yes” to “No”.

The overview page still showed the database as being Multi-AZ for a few minutes. Eventually it changed to “No” indicating the change had taken place. I opted to have the changes take effect immediately but it still took a few minutes.

While I did this little test, I remained logged into the MySQL CLI to see if I’d be kicked out during the change. I wasn’t.

Warning, I did this test with no data loaded into MySQL so I don’t know if there would be an outage if there was significant data in the database. I suspect not but can’t say for sure.

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