Amazon RDS Overview

RDS stands for Relational Database Service

• It’s a managed DB service for DB use SQL as a query language.

• It allows you to create databases in the cloud that are managed by AWS.

  • Postgres

  • MySQL

  • MariaDB

  • Oracle

  • Microsoft SQL Server

  • Aurora (AWS Proprietary database)

Advantage over using RDS versus deploying DB on EC2

• RDS is a managed service:

  • Automated provisioning, OS patching

  • Continuous backups and restore to specific timestamp (Point in Time Restore)!

  • Monitoring dashboards • Read replicas for improved read performance

  • Multi AZ setup for DR (Disaster Recovery)

  • Maintenance windows for upgrades

  • Scaling capability (vertical and horizontal)

  • Storage backed by EBS (gp2 or io1)

• BUT you can’t SSH into your instances

RDS – Storage Auto Scaling

• • Helps you increase storage on your RDS DB instance dynamically

• When RDS detects you are running out of free database storage, it scales automatically

• Avoid manually scaling your database storage

• You have to set Maximum Storage Threshold (maximum limit for DB storage)

• Automatically modify storage if:

  • Free storage is less than 10% of allocated storage

  • Low-storage lasts at least 5 minutes

  • 6 hours have passed since last modification

• Useful for applications with unpredictable workloads

• Supports all RDS database engines (MariaDB, MySQL, PostgreSQL, SQL Server, Oracle)

RDS Read Replicas for read scalability

• Up to 5 Read Replicas

• Within AZ, Cross AZ or Cross Region

• Replication is ASYNC, so reads are eventually consistent.

• Replicas can be promoted to their own DB.

• Applications must update the connection string to leverage read replicas.

• You have a production database that is taking on normal load.

• You want to run a reporting application to run some analytics.

• You create a Read Replica to run the new workload there.

• The production application is unaffected.

• Read replicas are used for SELECT (=read) only kind of statements (not INSERT, UPDATE, DELETE)

RDS Read Replicas – Network Cost

RDS Multi - AZ

Note: The Read Replicas be setup as Multi AZ for Disaster Recovery (DR)

• SYNC replication

• One DNS name – automatic app failover to standby

• Increase availability.

• Failover in case of loss of AZ, loss of network, instance or storage failure

• No manual intervention in apps

• Not used for scaling

RDS – From Single-AZ to Multi-AZ

• Zero downtime operation (no need to stop the DB)

• Just click on “modify” for the database.

• The following happens internally:

  • A snapshot is taken.

  • A new DB is restored from the snapshot in a new AZ.

  • Synchronization is established between the two databases.