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DR

1. Intro

  • Disaster
  • event that has a negative impact on a company’s business continuity or finances
  • Disaster Recovery
  • preparing for and recovering from a disaster.
  • type:
    • On-premise => On-premise
    • On-premise => AWS Cloud: hybrid recovery
    • AWS Cloud Region ` => AWS Cloud Region B

2. Key terms

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RPO: Recovery Point Objective

  • taking backup in one hr, so if D happens, then can take restore from backup/point taken an hr ago.
  • so rpo is 1hr here.
  • 1 min is expensive than 1 hr
  • low RPO === expensive

RTO: Recovery Time Objective

  • D happened, it took 2 hour to recover.
  • there was downtime of 2 hr
  • 15 min is expensive than 2 hr.
  • low RTO === expensive

3. Strategies to optimize RPO/RTO

a. backup / restore

  • DB:
  • RDS (single-region) --> 1hr --> backup/snapshot --> S3(not directly accessible) in same region (az-1 and az-2)
  • DR happens > az-1 goes down.
  • recreate infra using IAC + R53
  • or recover db from s3 snapshot (az-2 must have it)
  • if region has outage.
    • use cross region replication for rds
    • or use Aurora --> have read Replica/s in other region
    • or use global aurora --> have read Replica/s in other region ( < 1 sec)
    • and promote aurora read replica as primary in DR.
  • have your IAC ready, run it on DR
  • code/app deploy : take AMI + docker images
  • RTO is high, since getting up whole thing from scratch.
  • RPO is 1hr here.

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b. Pilot light

  • A small version of the app (critical business workload) is always running in different region.
  • update r53 to switch, on DR.
  • continuously replicate critical db to this region.

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c. warm light

  • Full but scaled-down version of your system, up and running in different region
  • Upon disaster, just scale up to production load

d. multi site

  • active - active
  • Full Production Scale is running AWS and On Premise
  • on D, it will inactive - active.
  • no recovery need to do.
  • RTO is in second/min
  • expensive

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4. DR tips

  • Backup
  • 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 a recovery from Direct Connect

  • Use ASG, ALB

  • Automation

  • CloudFormation / Elastic Beanstalk to re-create a whole new environment
  • Reboot EC2 instances with CloudWatch if alarms fail
  • AWS Lambda to automation to build infra, etc

  • IAC / terraform

  • on-prem tips

  • aws:ec2-i1 <> import/export <> on-prem:vm-1 
    - aws Amazon AMI 
  - download .iso file
  - then run AMI on on-prem, 
    - with hyper-v, virtual-box, etc.