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RDS

3 min read

  • Stands for Relational Database Service
  • A managed DB service, use SQL
  • It allow to create db that are managed by AWS
    • PostgreSQL
    • MySQL
    • MariaDB
    • Oracle
    • MsSQL
    • IBM DB2
    • Aurora (AWS proprietary)

Advantages

You can convert an EC2 instance to a database, but what are the advantages of RDS?

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

You can’t SSH into your instances

RDS - Storage Auto Scaling

Dynamic storage increase. RDS detects you are running out of space, and it scales automatically

Read Replicas

It is the replication for reading purpose.

  • up to 15 read replicas
  • Within AZ, cross AZ, cross region
  • Replication is ASYNC, reads are consistent
  • These replicas can be promoted to their own DB

Use Cases

On top of an ongoing production database, if you want to run a reporting application to run analytics, it will overrun the database and slow down. Thus, creating a read replica fixes this problem

Note: Read replicas are only used for SELECT statements

Network Cost

For RDS read replicas within the same region, you don’t pay cross AZ or cross-region fee

Multi AZ (Disaster Recovery)

It uses SYNC replication

  • One DNS name - automatic app failover to standby
  • NOT USED FOR SCALING. The backup DB is not used. It activates only when master fails

Common Exam Questions

  • The Read Replicas can be setup as Multi AZ for Disaster Recovery (DR)
  • To transfer an RDS from Single-AZ to Multi-AZ, you have to click “modify” and chose multi-AZ option. It is a zero downtime operation.

RDS Custom

Managed Oracle and Microsoft SQL Server Database with OS and database customization

  • RDS: Automates setup, operation, and scaling of database in AWS

  • Custom: access to the underlying database and OS so you can

    • Configure settings
    • Install patches
    • Enable native features
    • Access the underlying EC2 Instance using SSH or SSM Session Manager

  • De-activate Automation Mode to perform your customization, better to take a DB snapshot before

  • RDS vs. RDS Custom:

    • RDS: entire database and the OS to be managed by AWS
    • RDS Custom: full admin access to the underlying OS and the database

RDS Proxy

Fully managed db proxy for RDS.

  • Allows apps to pool and share DB connections to increase efficiency. Reduced RDS & Aurora failover time by up to 66%
  • Serverless, autoscaling, highly-available (multi-AZ). Supports RDS and Aurora
  • Can do IAM enforcement, requires no code change (mostly), and is never publicly accessible (must be accessed from VPC) Lambda

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