Sql-server – Create a New AWS RDS Instance of only one database from a snapshot

Changing Instance Class:

From the documentation "Modifying a DB Instance and Using the Apply Immediately Parameter", changing the instance class and setting "Apply Immediately" to false will result in:

• The change being applied during the next maintenance window.
• The change causing an outage to occur.

Since the instance is Multi-AZ and you're changing the instance class, your outage will be minimized to the amount of time it takes to failover to the standby replica. That isn't very long; likely worst-case a minute or two. You won't lose data that is already in the DB. Any existing connections will be dropped during failover. You should verify that applications connected to your database can withstand these conditions, or alternatively take them down for maintenance during this time.

Identifying RDS instance storage capacity:

You can identify how much of the RDS storage is currently in use by either:

1) Simply selecting your RDS instance from the RDS web console and viewing the "Storage" bar under the "Monitoring" header.

2) Viewing the "FreeStorageSpace" RDS cloudwatch metric for your RDS instance.

Further Reading:

• RDS Documentation - Viewing DB Instance Metrics

This is a good question,
working in cloud environment is tricky sometimes.

You can use pg_dumpall -f dump.sql command, that will dump your entire database to a SQL file format, In a way that you can reconstruct it from scratch pointing to other endpoint. Using psql -h endpoint-host.com.br -f dump.sql for short.

But to do that, you will need some EC2 instance with some reasonable space in disk (to fit your database dump). Also, you will need to install yum install postgresql94.x86_64 to be able to run dump and restore commands.

See examples at PG Dumpall DOC.

Remember that to keep integrity of your data, it is recommended (some cases it will be mandatory) that you shutdown the systems that connect to the database during this maintenance window.

Also, if you need speed up things, consider using pg_dump instead pg_dumpall, by taking advantage of parallelism (-j njobs) parameter, when you determine the number of CPUs involved in the process, for example -j 8 will use until 8 CPUs. By default the behavior of pg_dumpall or pg_dump is use only 1. The only advantage by using pg_dump instead pg_dumpall is that you will need to run the command for each database that you have, and also dump the ROLES (groups and users) separated.

See examples at PG Dump DOC and PG Restore DOC.