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Amazon RDS

Updated Jul 26, 2020 ·
NOTES

This is not an exhaustive documentation of all the existing AWS Services. These are summarized notes that I used for the AWS Certifications.

To see the complete documentation, please go to: AWS documentation

Overview​

Amazon RDS is a managed database service for relational databases

  • Provides cost-efficient, resizable capacity
  • AWS manages common database administration tasks.
  • AWS provisions an EC2 instance behind the scenes and EBS Volume

DB Engines supported​

A DB engine is the specific relational database software that runs on your DB instance. Amazon RDS currently supports the following engines:

  • MySQL
  • PostreSQL
  • Oracle
  • Microsoft SQL Server
  • Aurora
  • MariaDB

Advantages and Disadvantages​

Advantages:

  • Security through IAM, security groups, KMS, SSL.
  • Backup/Snapshot/Point in time restore functionality.
  • Support for multi AZ deployment.
  • Read replicas.
  • Monitoring happens through CloudWatch.
  • Managed and scheduled maintenance.
  • Pay per hour based on provisioned EC2 and EBS.
  • Scaling capability (vertical and horizontal).
  • Storage backed by EBS (GP2 or IO).

Disadvantages:

  • No SSH into the instance which hosts the database.

Use cases​

  • Store relational datasets.
  • Perform SQL queries.
  • Transactional inserts, deletes, updates.

RDS Backups​

Backups are automatically enabled in RDS. AWS RDS provides automated backups:

  • Daily fill backup of the database (during the maintenance window).
  • Transaction logs are backed-up by RDS every 5 minutes which provides the ability to do point in time restores.
  • There is a 7 day retention for the backups which can be increased to 35 days.

DB Snapshots:

  • There are manually triggered backups by the users.
  • Retention can be as long as the user wants.
  • Helpful for retaining the state of the database for longer period of time.

RDS Read Replicas​

Read replicas helps to scale the read operations.

  • We can create up to 5 read replicas
  • These replicas can be within AZ, cross AZ or in different regions
  • The data between the main database and the read replicas is replicated asynchronously - reads are eventually consistent
  • Read replicas can be promoted into their own database
  • Read replicas are used for SELECT operations (not INSERT, UPDATE, DELETE)

Use case for read replicas:

  • Production database is up and running taking on normal load
  • There is a new feature for running some reporting for analytics which may cause slow downs and may overload the database
  • To fix this we can create read replicas for reporting

Network cost for read replicas:

  • In AWS there is network cost if data goes from one AZ to another
  • In case of cross AZ replication, additional costs may incur because of network traffic
  • To reduce costs, we could have the read replicas in the same AZ

RDS Multi AZ (Disaster Recovery)​

  • RDS Multi AZ replication is done using synchronous replication.

  • In case of multi AZ configuration we get one DNS name.

  • In case of the main database goes down, the traffic is automatically re-routed to the failover database.

  • Multi AZ is not used for scaling.

  • The read replicas can be set up as Multi AZ for Disaster Recovery.