Overview

• RDS stands for Relational Database Service

• It is 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
  • IBM DB2
  • Aurora (AWS Proprietary database)

Advantage over using RDS vs 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 Disaster Recovery
  • Maintenance windows for upgrades
  • Scaling capability (vertical and horizontal)
  • Storage backed by EBS

• BUT you CAN NOT SSH into your instance

Storage Auto Scaling

• Help 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 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

RDS Read Replicas vs Multi AZ

RDS Read Replicas for read scalability

• Up to 15 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

• Application must update connection string to leverage read replicas

RDS Read Replicas - Use Cases

• You have a production database that is taking on normal workload

• 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

• In AWS there is a network cost when data goes from one AZ to another

• BUT For RDS Read Replicas within the same region, you don't pay that fee

RDS Multi AZ (Disaster Recovery)

• SYNC replication

• One DNS name - automatic app failover to standby

• Increase availability

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

• No manual intervention in apps

• Not used for scaling

*What I noted: *

• Increase read workloads -> Read Replicas. Increase High Availability and disaster recovery -> Multi AZ

• Read Replicas is ASYNC replication (read eventually consistent). Multi AZ is SYNC replication.

• Read Replicas (manual). Multi AZ (automatically)