Western Digital has just issued this statement in response to our feedback. Here it is:
WD has learned that initial production units of WD Red 5* and 6 TB drives perform below our expectations in random-read benchmark tests when measured with specific testing software. We have found a configuration setting to be causing these particular test results, for which we are developing a firmware update to correct the configuration setting. In the intended application -- multi-drive NAS systems -- the drives have performed to our high expectations in WD’s labs and by our system partners; users will experience normal WD Red performance.
WD is committed to providing optimally performing storage products, designed for intended applications, and we will have a firmware update available through the WD Red Product Customer Service support line as it becomes available.
*Limited quantities of 5 TB have shipped with the earlier configuration setting.