Recovery Time Objective (RTO)
The time it takes after a disruption to restore a business process to its service level, as defined by the operational level agreement (OLA) . Simply how much time will take to restore the service.
Ex: if a disaster occurs at 12:00 PM (noon) and the RTO is eight hours, the DR process should restore the business process to the acceptable service level by 8:00 PM
Recovery point Objective (RPO)
The acceptable amount of data loss measured in time.
Ex: if a disaster occurs at 12:00 PM (noon) and the RPO is one hour, the system should recover all data that was in the system before 11:00 AM. Data loss will span only one hour, between 11:00 AM and 12:00 PM (noon)
How to decide RTO & RPO
A company typically decides on an acceptable RTO and RPO based on the financial impact to the business when systems are unavailable.
The company determines financial impact by considering many factors,such as the loss of business and damage to its reputation due to downtime and the lack of systems availability.
IT organizations then plan solutions to provide cost-effective system recovery based on the RPO within the timeline and the service level established by the RTO
Ex: A share market trading website can not have same RPO with online book or entertainment site. Because in trading every seconds lot of live transaction will happen
As most important to get less RTO & RPO ,at the same time need to spend more money .Its depend on how you setup HA & DR environment.