The Low object data storage alert monitors how much space is available for storing object data on each Storage Node. It is related to the Storage Status (SSTS) alarm, but it is not exactly equivalent.
By default, a major alert is triggered when this condition evaluates as true:
(storagegrid_storage_utilization_data_bytes/ (storagegrid_storage_utilization_data_bytes + storagegrid_storage_utilization_usable_space_bytes)) >=0.90
If a major or minor Low object data storage alert is triggered, you should perform an expansion procedure as soon as possible.