Hello, thank you all for your replies.
So I will explain my current setup :
tr-004 is attached to my qnap TS 453s pro via a usb-C to usb-A 3.2 gen1 as required by the documentation ( not the original cable of the tr-004 though - this one is 1meter long - I bought tr-004 secondhand without the cable;
tr-004 is set as raid 10 ( software mode ) with four 3.5 inch ironwolf 4tb disks inside.
the NAS is raid 5 with 4 WD red 2.5 inch 1TB drives. - plugged to the router via rj45
The tr-004 is set as external drive ( didn’t manage to set it as the NAS extension )
On windows 11, my nas can be seen on the network as a network computer ( I logged in as admin once ) and I have access to all folders. the NAS folders are captioned on WINDOWS as “default drive shares”, and the tr-004 also appears, this time as “esata storage share”.
So if i’m not mistaken data from windows to the tr-004 uses the network ( I have a recent rj45 cat6 cable plugged in to my router as well as an active wifi connection, with both handled by "killer intelligence center ) to access the nas then the above mentioned cable from the nas to the tr-004. Maybe this explains the low 30mb/s speeds.
One more test with the 383 mo file ( mp4 format)
Note : all the tasks below executed from within windows explorer
tr-004 to nas : 90 - 100 mb/s
Nas to tr-004 : 180 mb/s !
( these tasks seem faster to execute from windows than from filestation…)
Windows to tr-004 : around 60mb/s
Windows to qnap : briefly reached 70 mb/s ( average around 60 mb/s I’d say)
Tr-004 to windows : around 30-35 mb/s
NAS to windows : slightly slower 28 mb/s