Comment by ployable7

I’m not saying you can’t blend the numbers, I’m saying you shouldn’t blend the numbers. Because one number doesn’t communicate what you actually need to know to build.

You want to know how reliable the service is in steady state. For example it’s useful to know that S3 is effectively lossless in steady state whereas EBS volumes have an AFR of about 0.1%. You build your apps very differently between S3 and EBS knowing this. You can build highly resilient applications on each, but you code them differently, informed by these design goals.

You separately want to understand the failure modes that will require you to fully recover from backup. For example knowing that cloud storage is resilient to everything but region failure would inform you that your backups should be out of the region, not just a bucket in the same region. You don’t get that perspective from just a 9s number.