Windows 10: copy sata to sata disk speed drops after few seconds

Hi,

I have a pc recently upgraded z390 designare, 64 GB ram 2133, i9900k where I installed 2 hd 8TB barracuda.

I am using the two disks as mirror, but not raid, folders are update with a 3rd party software, run manually when I need to.

Copying the contents of the first drive to the second has been a pain. It starts at about 150-160 MB/s then, after a bunch of seconds, maybe little less than a minute, speed drops to something around 50-60 MB/s, and often has drops, lasting minutes, to few MB/s.

I am using Teracopy. I tried to turn off defender, no other antivirus/firewall installed. I turned off indexing and optimized both disks. A test with a Live! installation of ubuntu gives 130-140 MB/s as average for the same transfer between the two disks. Peaks are at 170-180 MB/s, which is the top speed from several disk benchmarks. I tried to plug the sata cables to different ports not all are available as I have also a graphics card installed which uses few lines in common with sata ports. Also tried different cables.

Testing software from seagate or others gives healthy status of the system. Overall benchmarks are very good.

What's happening???

Thank you for any hint.

:)

 

Error connecting SATA disk to Windows 10 using a SATA to USB harness

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It won't let me reactivate as it says it can't do this on an invalid Disk Pack. If I go to use Convert to Basic Disk it says I will loose data. This disk was the Disk 0 bootable disk for Windows 7. So it will have a boot sector and and a reserved section
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Low speed sata copying

Hello,
Firstly, i have a problem with hard disk (partition dissapearing while copying) after this i installed the SATA/AHCI intel chipset drivers. Now it's fine but copy speed is very low.
Look this video: first part from Seagate HDD to a SSD then from Seagate HDD folder to other folder on same HDD.
And here is a screenshot from HD Tune: https://i.gyazo.com/cc0acd8281715ffb86132d5783e0bedf.png
What is wrong?