Windows 10 extreme slow in writing to UEFI RAID5.

ATTO Disk Benchmark shows this for my Asrock Z370 Killer SLI with 4x HGST HUH728080ALE604

The mainboard does the RAID. So Windows only sees one disk. I can't understand the mega difference in speed in reading and writing.



This is what the task-manager tells me. 100% load? Come on...



This was a sequential copy from the NAS to the freshly installed and empty local drives. According to the specs, the read and write-speed should be way closer. Closer to the read-speeds.

And to make the confusion complete, Cristal Disk Benchmark tells me this:



The network should be the bottleneck at 1Gbit/s. Why is the disk array taking this honor?

Thanks in advance for any comment that leads to the solution of this problem.

I don't have any specific experience with RAID 5 on an Intel controller, only on ultra high end RAID systems, so my experience won't really translate to this scenario well, but what strikes me is that average response time is almost 3 seconds (wow!). Some things to consider:

1) Do you have the appropriate Intel drivers installed that match with the BIOS RAID config for your system?

2) Is it possible that there is one drive that is at fault slowing the whole array? You might want to see if Performance monitor shows any issue with one specific disk in the array. Again, my lack of unfamiliarity with the Intel RAID may show here. Hopefully the counters are available in Perf Mon to allow you to monitor the individual drives within the array.

One other minor point: Don't confuse the 100% active time with 100% load. Yes, the 2 can often be related, but there is a difference. The 100% active time indicates that the system is busy servicing the array 100% of the time, but again, that could be just one disk while the other constituents are just loafing along under practically no load.

My apologies I could not help further, but hopefully this gives you at least something to investigate.