Description of problem (please be detailed as possible and provide log
snippests):
In order to calculate average usage and days left (until storage is full) we are relying on "ocs-metrics-exporter" "uptime": https://github.com/red-hat-storage/odf-console/blob/master/packages/ocs/queries/ceph-storage.ts#L338 which is incorrect ("uptime" of the exporter is not equal to the "retention period" of the Prometheus instance), it will affect the average if exporter is running for (say) a year (it is an ever increasing value).
Another issue is if exporter restarts for some reason, it gonna reset the "uptime" as well.

Version of all relevant components (if applicable):
ODF 4.16


Does this issue impact your ability to continue to work with the product
(please explain in detail what is the user impact)?


Is there any workaround available to the best of your knowledge?


Rate from 1 - 5 the complexity of the scenario you performed that caused this
bug (1 - very simple, 5 - very complex)?


Can this issue reproducible?
Yes, whenever "uptime" > "retention period" of Prometheus


Can this issue reproduce from the UI?
Yes


If this is a regression, please provide more details to justify this:


Steps to Reproduce:
1.
2.
3.


Actual results:


Expected results:


Additional info:
Epic: https://issues.redhat.com/browse/RHSTOR-4624.

Maybe we can look into reading retention period directly from the OCP ConfigMap (https://docs.openshift.com/container-platform/4.13/monitoring/configuring-the-monitoring-stack.html#modifying-retention-time-and-size-for-prometheus-metrics-data_configuring-the-monitoring-stack).