Hard Read Errors.

This shows the number of read errors that have occurred on a drive that could not be recovered by a physical drive's Error Correction Code (ECC) algorithm or through retries during the reference time (phyDrvRefTime). Over time, a disk drive may produce these errors. If you receive these errors, a problem may exist with your drive.

The value increases every time the physical drive detects another error.

The severity of these errors depends on whether the monitored system is running in a fault tolerant mode. With fault tolerance, the controller can remap data to eliminate the problems caused by these errors. In either case, if you see an increase in these errors, schedule server down time to run diagnostics to verify that a problem exists.