When designing a solution, what defines the maximum tolerable amount of data loss from an IT service due to a major incident?

SLO (Service Level Objective) is a specific measurable performance target defined within a service level agreement, such as 99.9% availability, and does not specifically quantify the maximum acceptable data loss.

RPO (Recovery Point Objective) specifically quantifies how much data loss an organization can tolerate by defining the maximum age of data that must be restored from backup or replication after a disaster - for example, an RPO of 1 hour means at most 1 hour of data can be permanently lost. This metric is distinct from recovery speed and directly determines backup frequency and replication lag requirements. It is established during business impact analysis and drives storage and data protection architecture decisions.

SLA (Service Level Agreement) is the broader contractual document between a provider and customer that may contain RPO and RTO commitments, but is not itself the metric defining maximum data loss.

RTO (Recovery Time Objective) defines the maximum acceptable duration of service downtime following an incident - how quickly the service must be restored - which measures time-to-recovery rather than data loss tolerance.