I ve disable SMB Direct on WIN11, and activate SMB 1.0.
Same problem. I ve now also lost SSH conection by putty, after the computer reboot. 
SSH access should not be reliant on the SMB version
Ok but what can I do to get it up ?
try a reboot of the NAS
Ok, after reboot, i can connect in SSH, I ve rollback to SMB 2.1. You can close this topic. I conclude that since the SMB protocole update has been passed, I lose speed on this NAS. Not great. Thanks for investing and help.
If you feel it’s necessary, you can also open a ticket with us via our Helpdesk or the Community. Our Support team may be able to analyze your situation and offer suggestions.
I have a retired-this-year but was still working NAS of a similar age and I would expect more speed than that at any SMB level. Is the NAS itself encrypted, as that will also slow it down?
I’d look through the log for hints (do a transfer and check both the NAS and Windows logs for that period). Also check the SMART data for the drive in case that is unhappy. Plus use the Windows Task Manager to see what tasks seem busy during the transfer (in case it’s something like Anti-Virus).
I also forgot to mention change your cables to cat8 to the latest data standard 40gb/ps & also apply static ip on your switch and set jumbo frames to 9000 & mtu to 1518 & all should be well you have to set all three parts up to the same apart from ip addresses or they will clash & not work you should find it will speed up then.
You are using both ports on your NAS? Those are for port aggregation or routing. If you want port aggregation you need a router that supports that. Food for thought.
Uhm, first of all, you don’t need cat8 and nothing will be at 40Gbps unless you have a switch and NICs capable of that. Setting Jumbo Frames is setting the MTU. If you set one device on the network to 9000 and another to 1518, you will have problems as packets with an MTU size of 9000 won’t be able to get through a NIC with an MTU of 1518. It’s like trying to get a huge box of stuff through a door that is smaller than the box.
Static IP on the switch also has nothing to do with transfer rates. Unless the user is using a managed switch, there’s no way to set static IP on it.
If you have another computer on your network, do a file transfer with that and see what LAN speed you get. That will establish what throughput your network hardware is capable of producing.
I have a QNAP TS-230, which like yours uses an ARM processor. I only use my NAS for file storage, so turned off as many services as I could. Still, the TS-230 is not a fast device. I eventually got a TS-253A, which has an X86 CPU, and it is much faster; I repurposed the TS-230 as a backup to that.
If your test proves your network can produce faster transfers, then try disabling services on your NAS that you don’t use. That will reduce load and also free up memory.
One of the best ways to test your speed is to download the AJA System Test Light app at AJA System Test: Accurately Test Your System performance and speed
This is what QNAP shows in some of their information for test speeds.