I've been thinking about defining some infrastructure-independent metrics for SLA requested by customer.
The developed software is being deployed on-premise within customer's DC and managed by customer's technical staff, - therefore I cannot give any numerical reliability guarantees related to infrastructure (Availability/Fault-tolerance), - this must be stated in the sales agreement.
Another point here - is that both availability and FT form not just of infrastructure and operational aspects, but also of the software quality (it's architecture), which leads to the question -- is it feasible if I defined infrastructure-independent availability and FT somehow (just for developed software in conjunction with underlying applications, like k8s, OS, DBs etc.)? If so, is it ok to use same metrics (availability %%; RPO; RTO; something else?)?
Perhaps there are some books or articles describing my case?