WD Red HDD read speed below 1 MB/s?


I have a WD Caviar Red 4 TB drive that reads at speeds below 1 MB/s. It goes up to maybe 7 MB/s, and occasionally spikes up to 10 MB/s or 20 MB/s at its best. I’m not sure what’s wrong with it. But this started recently… I think… since I installed Windows 10. Yes, I have it installed in a tower PC. I use it for storage though, and a Samsung SSD for the system.

Are there any known compatibility issues between Windows 10 and WD Red drives? It’s not very old and it has worked perfectly fine under Windows 8.1.

Is there any chance that the disk simply is not spinning up properly? I think I hear it spin up sometimes, very intensely. I have several disks, so it’s hard to tell which one it is. But there is no grinding noise or anything like that. None that I recognize anyway, or that I can hear.

Is it possible to read the spindle speed via the SATA interface? Is there any pre-built tool for that? I wouldn’t want to build it myself. Perhaps the WD diagnostic tool has such feature? That would be a great tool to have.

The disk actually jumped up to 120 MB/s yesterday. But it doesn’t want to do it again today.

The model is WD40EFRX.

The disk appears in BIOS, in Explorer, I can explore the content, read files from it. It appears to be normal. But this reading speed is embarrassing! I haven’t tested doing a write operation because of fear of data loss.


I recommend running a diagnostic using WD DLG.

Data Lifeguard Diagnostic for Windows

I almost have it figured out now. It’s either one or both of these two things: a bad Seagate HDD, and/or bad Windows 10. I have disconnected all drives except the WD Red and Samsung SSD. However, the bad Seagate HDD drive alone can’t be the sole cause. They are all on the same Intel SATA controller and for example a WD Black was reading OK whilst the bad Seagate HDD was connected. I also have another identical Seagate that was not affected.

For some reason, the WD Red just doesn’t seem to like one or more of the other drives. I just haven’t figured out yet which one. I also have to try Linux and Windows 7. I know Windows 10 comes with its own set of problems that can cause any number of seeming unrelated issues.

I have the WD Red reading at 125 MB/s right now.

That’s good enough for me. Now I can do scans, and backup data and everything else. But I’m sure it’s safe to continue using this disk. However I will do a complete scan, just in case. I was not so keen on doing a 14 days scan at 1 MB/s.

OK, I have the drive reading at 140 MB/s right now on another PC. I am doing an extended scan. But before I removed it from the original PC, I did a quick test with DLGDIAG and got mixed results. I got two PASS messages and one FAIL message.

Test Option:

Model Number:
WDC WD40EFRX*********

Unit Serial Number:

Firmware Number:

4000.79 GB

SMART Status:

Test Result:

Test Error Code:
06-Quick Test on drive 2 did not complete! Status code =
02 (Interrupted by hard or soft reset), Failure Checkpoint = 98 (Unknown Test)
SMART self-test did not complete on drive 2!

What does status code 2 indicate? What is checkpoint 98? What is “unknown test” supposed to mean? The name of the test is “quick test”, is it not? Why the silly name of “unknown test” then? Is this in fact an unknown error instead?.. but then it should say so in the message… no? Also, why does it say that SMART self-test did not complete? If it didn’t complete, how did it PASS??? Is the first one just an indicator that SMART is enabled, or what???