Question NVME to SSD slow but SSD to NVME fast

[baburaoapte]

Okey, so let's see if we can figure this out. I have samsung 970 plus 250GB NVMNE on which my windows 10 is and then I have Samsung 840 EVO 120GB as an internal storage drive. They're both pretty much empty (fresh install). Now when I transfer a 16GB folder containing copies of ISOs from NVME to my SSD, it starts out high for like 2 seconds and then gradually drops down to 144MBps after the first 30% transfer. However, when I transfer the same file from SSD TO NVME, consistent file transfer above 400 MBps. WHY??? This is SO annoying. Please, help me out here. Another thing to let you know, both benchmarked and shows appropriate write/read speed. Both drives are updated. Mobo is also updated to latest BIOS. Everything is updated! I have attached 4 images. First two are NVME (OS) to SSD (Storage). Last two are SSD (Storage) to NVME (OS).
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[SkyNetRising]

You're seeing limitations of 840 evo there.
1st two is 840 evo sequental write performance, 2nd two is 840 evo sequental read performance.

https://www.anandtech.com/show/7173...w-120gb-250gb-500gb-750gb-1tb-models-tested/4

 

[baburaoapte]

Well, okey I understand the chart. Now, how do I explain this? LOL. This is from SSD (120GB) to USB 3.0 HDD (1TB). Took 2:40 minutes... SSD to SSD took 2:43. WHAAA? lol
Image 5

And did another test SSD to HDD (320GB very very old HDD) and time was 2:55 minutes.