cpqDaPhyDrvThrHardReadErrs is the factory-set maximum threshold for uncorrectable read errors on a physical drive during its reference time window, corresponding to the cpqDaPhyDrvHardReadErrs counter. Once a drive's actual hard read error count approaches this threshold, the controller and management software treat it as a strong signal the drive needs replacement. For example, if a drive's hard read error counter climbs to just below this threshold, an admin would proactively schedule its replacement rather than waiting for the threshold to actually be crossed.