Surface Read Test duration variations = normal?

[Mastakilla]

Hi,

I have 8x WD DC HC510 10TB HDD. All have the same firmware (38Q). But still I'm seeing quite large differences in the Read Test duration:

14h53m44s
15h03m06s
14h10m30s
14h27m58s
14h21m05s
14h37m47s
14h30m56s
14h17m12s

To make sure the difference wasn't because of my system usage during the test, I ran it a 2nd time for the 2nd HDD:
15u03m15s (vs 15u03m06s)

I'm wondering: is this normal? Are the 1st and 2nd HDD then "weaker" HDDs?

All are factory-reset/emptied refurbished HDDs btw...

[hdsentinel]

Yes, I can confirm that it is completely normal.
Even disk drives of the same model, same firmware and same production may have minor differences in performance.

If you open the Information page in Hard Disk Sentinel, you may see that the "Extended self test time" values of your drives are different.
Those extended self tests run completely "inside" the hard disk drives, with no data transfer - so that confirms that the disk drives internally has slightly different performance, which are not affected by operating conditions, for example not affected/limited by motherboard chipset, controller, driver, docking station etc.

[Mastakilla]

Thanks for the confirmation!

I wasn't aware there was such a big difference possible (6% difference between the fastest and the slowest I've just calculated)...
But I guess I'll manage to live with it