The DR plan

Disaster recovery (DR) is a concept different to backup. Backup is obviously part of the DR plan but is not the only component.

Disasters can have many causes and can affect many services. The first step is to identify all of the key services. These will include for example

  • Domain controllers (usernames, passwords, computer names, DNS, DHCP etc etc)
  • Medical software servers
  • Imaging servers
  • Shared resources
  • Scanned documents
  • Router and switch configurations
  • Dictation audio files
  • Business emails
  • Business financial records

Some enumeration of the potential disasters

  • Hard Drive Failure
  • File corruption
  • Ransomware attack
  • Individual computer failure eg Power supply, motherboard, network card
  • Multiple computer failure eg fire, water damage (sprinklers), theft

Then some thought is required about the RTO and RPO time points.

Recovery point objective (RPO) is the point to which the system can be recovered. If the last backup was 10 days ago, then this is the RPO

Recovery time objective (RTO) is the time taken to restore the system from the disaster. If it takes 4 days to get a new server installed and configured then the RTO is 4 days. The time to diagnose the problem needs to be added to the RTO

The RTO increases in cost very quickly with reducing time. The RPO has an increasing system performance cost but not as much of a dollar cost with reducing time. Backups can be done 5 minutely but will slow the system appreciably.