6TB Drives With Different SMART Extended Test Time, Any Threories?


So I just purchased four HGST 6TB drives P/N: 0F26900 and all manufactured in AUG 2017, all with the same firmware 7JHN, basically all the numbers are identical except the serial numbers of course.

Here is the discrepancy which catches my eye, the time it takes to complete a SMART Extended Test:

S/N: XXXXXLBD = Firmware says 825 minutes (Actual test time < 14 hours)
S/N: XXXXXWLD = Firmware says 825 minutes (Actual test time < 14 hours)
S/N: XXXXX848 = Firmware says 780 minutes (Actual test time < 13 hours)
S/N: XXXXXW4D = Firmware says 976 minutes (Actual test time < 16 hours)

So why the large discrepancy?

I just find it odd that there are some extremes here knowing that all the drives are the same model. Are we looking at a rotational speed issue? Head actuator speed issue? The thing is, all of my previous hard drives always had the same test times, this is the first time I’ve ever seen this kind of discrepancy.