Disaster Recovery

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

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
All AWS Multi Region

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

Ability to download Amazon Linux 2 AMI as a VIM (iso format)
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)
AWS Server Migration Service (SMS):
- Incremental replication of on-premise live servers to AWS

Is my AMI copied across multiple regions? Is it stored in the parameter store?
Is my CloudFormation StackSet working and tested to work in another region?
What is my RPO and RTO?
Are Route 53 Health Checks working correctly? Tied to a CW Alarm?
How can I automate with CloudWatch Events to Trigger some Lambda functions and perform an RDS read replica promotion?
is my data backed up? What is the RTO and RPO of my data?

EFS Backup:
- AWS Backup with EFS: it is a managed service, we can set the frequency, backup time, retain time, lifecycle policy
- EFS to EFS backup in the same region
Route 53 Backup:
- We can use ListResourceRecordSets API for exports
- We can write our own script for import into Route 53 or other DNS provider
Elastic Beanstalk Backup:
- We can save configuration files using the eb cli or AWS console

We can download Amazon Linux 2 AMI as a VM (.iso format)
VM Import/Export:
- We can migrate existing applications into EC2
- We can create a DR repository strategy for on-premise VMs
- We can export back the VMs from EC2 to on-premise
AWS Application Discovery Service:
- Gather information about on-premise servers to plan a migration
- Server utilization and dependency mappings
- We can track migration with AWS Migration Hub
AWS Database Migration Service (DMS):
- Replicate on-premise databases into AWS and vice-versa
- Works with various databases technologies such as Oracle, MySQL, DynamoDB, etc.
AWS Server Migration Service (SMS):
- Incremental replication of on-premise live servers to AWS