Skill 4.2: Design a disaster recovery solution
Whereas high availability is concerned about mitigating against different types of failures, disaster recovery is concerned about what to do in the case of a failure occurring. A disaster recovery solution involves technology and processes that will enable you to restore your availability with an appropriate data loss in an appropriate timeframe.
To design an appropriate disaster recovery plan, you need to engage the appropriate stakeholders in your organization to articulate the following requirements:
Recovery Time Objective (RTO)
Recovery Point Objective (RPO)
Recovery Level Objective (RLO)
When designing your disaster recovery plan you need to take in multiple additional factors, including:
The size of the databases
How long it will take to restore hardware
Whether you can take advantage of the cloud
How long it will take to restore the Windows operating system
How long it will take to restore the SQL Server environment
The order in which you will need to perform the various tasks in your disaster recovery plan
These considerations and others were covered in depth in Chapter 2. Make sure you understand the concepts and considerations covered there, because they will impact your high availability design. The exam might ask you to design a high availability and disaster recovery solution for the same given scenario.
In a lot of organization’s cases their database solutions are “too big to fail.” In such cases you need to rely more on high availability, redundancy, and processes to ensure that you never have to recovery from a disaster. Good luck!