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Disaster Recovery

Links: 101 AWS SAA Index

RPO and RTO

  • RPO → Recovery Point Objective
    • It is basically how often you run backups, how back in time can you recover.
    • RPO is how much of data loss are you willing to accept in case of a disaster.
  • RTO → Recovery Time Objective
    • Defines the down time after disaster.
  • RPO and RTO visualised
    • attachments/Pasted image 20220430153011.jpg
Our target is to decrease the RTO and RPO
  • Cost increases as the try to decrease RTO and RPO.

DR Strategies

  • List of strategies with RPO and RTO in decreasing order.
  • Backup & Restore: RPO and RTO in hours.
    • It is quite cheap. We recreate infrastructure only when we have a disaster.
    • Very easy.
  • Pilot Light: RPO in minutes, RTO in hours.
    • A small version of the app is always running in the cloud.
    • Useful for the critical core (pilot light)
    • Faster than Backup and Restore as critical systems are already up
    • For example in the RDS will be running but not the EC2 instances so if some disaster strikes the on premise data centre then Route53 will manage the failover.
  • Warm Standby: RPO in seconds, RTO in minutes.
    • Full system is up and running, but at minimum size
    • Upon disaster, we can scale to production load
  • Multi Site/ Hot Site approach: RPO and RTO is almost 0.
    • Full Production Scale is running AWS and On Premise
To remember RPO and RTO RPO decreases first, left hand side since P < T so RPO < RTO.

Last updated: 2022-05-01