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AWS Disaster Recovery

Updated Aug 30, 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

Disaster​

  • Disaster: any event that has a negative impact on a company's business continuity or finances.
  • Disaster Recovery (DR) is about preparing for and recovering from a disaster.
  • Disaster recovery solutions:
    • On-premise to on-premise: traditional DR, expensive
    • On-premise to cloud: hybrid recovery
    • AWS Cloud Region A to AWS Cloud Region B

RPO and RTO​

  • RPO - Recovery Point Objective: How often we create backups. Time between the RPO and the disaster is the data loss.
  • RTO - Recovery Time Objective: The point in time when the recovery finishes. The time between the disaster and the RTO is downtime.

Disaster Recovery Strategies​

All strategies are available for Multi-region.

  • Backup and Restore

    • High RPO, cheap, easy to manage and accomplish.

  • Pilot Light

    • A small version of the app is always running in the cloud.

    • Useful for critical core (pilot light).

    • Similar to backup and restore strategy.

    • Faster than backup and restore as critical system are already running.

  • Warm Standby

    • Full system is up and running but at a minimal size.

    • Upon disaster we can scale to production load.

  • Hot Site / Multi Site Approach

    • Very low RTO - very expensive.

    • Full production scale is running on the cloud.

Disaster Recovery Tips​

-Backups

  • EBS Snapshots, RDS, automated backups, snapshots, etc.
  • Regular pushes to S3/S3 IA/Glacier, Lifecycle Policy, Cross region replication.
  • From on-premise: Snowball or Storage Gateway.

-High Availability

  • Use Route53 to migrate DNS over from region to region.
  • RDS Multi-AZ, ElastiCache Multi-AZ, EFS, S3.
  • Site to site VPN as recovery from Direct Connect.

-Replication

  • RDS Replication (Cross Region), AWS Aurora + Global Databases.
  • Database replication from on-premise to RDS.
  • Storage Gateway.

-Automation

  • CloudFormation/Elastic Beanstalk to recreate a whole new environment.
    • Recover/Reboot EC2 instances with CloudWatch if alarm is in fail state (ALARM).
    • AWS Lambda for customized automation.

-Chaos

  • Netflix has a "simian-army" randomly terminating EC2 instances.

On-Premise Strategy with AWS​

  • Download Amazon Linux 2 AMI as a VIM

    • iso format.
    • VMWare, KVM, VirtualBox, Microsoft Hyper-V.

  • VM Import/Export

    • Ability to migrate existing applications into EC2.
    • Ability to create a DR repository for on-premise VMs.
    • Ability to export back the VMs form EC2 to on-premise.

  • AWS Application Discovery Service

    • Gather information about on-premise servers to plan a migration.
    • Provides information about server utilization and dependency mappings.
    • Track all migrations with AWS Migration Hub.

  • AWS Database Migration Service (DMS)

    • Replicate on-premise.
    • Works with various DB technologies.

  • AWS Server Migration Service (SMS)

    • Incremental replication of on-premise live servers to AWS.

Database Migration Service (DMS)​

  • Quickly and securely migrate databases to AWS.
  • It is resilient and self healing.
  • The source database remains available during migration.
  • Supports:
    • Homogeneous migrations, example Oracle to Oracle.
    • Heterogeneous migrations, example: Microsoft SQL Server to Aurora.
  • Supports continuous data replication using CDC.
  • We must create an EC2 instance to perform the replication tasks.

DMS Sources and Targets​

  • Sources

    • On-premise and EC2 instance databases: Oracle, MS SQL Server, MySQL, MariaDB, PostgreSQL, MongoDB, SAP, DB2
    • Azure SQL Database
    • Amazon RDS: all including Aurora
    • Amazon S3

  • Targets

    • On-premise and EC2 instance databases: Oracle, MS SQL Server, MySQL, MariaDB, PostgreSQL, AP

    • Amazon RDS

    • Redshift

    • DynamoDB

    • S3

    • ElasticSearch

    • Kinesis Data Streams

    • DocumentDB

AWS Schema Conversion Tool (SCT)​

  • Converts a database schema form one engine to another. Example: OLTP (SQL Server, Oracle) to MySQL, PostgreSQL, Aurora; OLAP (Teradata or Oracle) to Redshift

  • We do not need to use SCT if we are migration from the same DB engine to the same DB engine