Download from NAS slower than upload to NAS

[Kubernetes]

My unraid NAS does have a Realtek onboard NIC:

[10ec:8168]03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 0c)

 

When I upload via SMB something from my computer to NAS I reach 114MB/s transfer speed (displayed in Windows Explorer)

When I download via SMB something from my NAS to my computer I reach only 85MB/s transfer speed (displayed in Windows Explorer)

 

When I perform iperf3 I get the following results, which matches to the upload transfer speed experience:

➜  ~ iperf3 -c NAS
Connecting to host NAS, port 5201
[  5] local COMPUTER port 49409 connected to NAS port 5201
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec   110 MBytes   920 Mbits/sec                  
[  5]   1.00-2.00   sec   111 MBytes   935 Mbits/sec                  
[  5]   2.00-3.00   sec   109 MBytes   917 Mbits/sec                  
[  5]   3.00-4.00   sec   112 MBytes   937 Mbits/sec                  
[  5]   4.00-5.00   sec   111 MBytes   934 Mbits/sec                  
[  5]   5.00-6.00   sec   111 MBytes   932 Mbits/sec                  
[  5]   6.00-7.00   sec   111 MBytes   934 Mbits/sec                  
[  5]   7.00-8.00   sec   111 MBytes   932 Mbits/sec                  
[  5]   8.00-9.00   sec   111 MBytes   929 Mbits/sec                  
[  5]   9.00-10.00  sec   110 MBytes   924 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-10.00  sec  1.08 GBytes   930 Mbits/sec                  sender
[  5]   0.00-10.01  sec  1.08 GBytes   926 Mbits/sec                  receiver

iperf Done.

 

When I do only reverse the result is matching my download transfer speed experience:

➜  ~ iperf3 -c NAS -R
Connecting to host NAS, port 5201
Reverse mode, remote host NAS is sending
[  5] local COMPUTER port 49782 connected to NAS port 5201
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec  86.2 MBytes   723 Mbits/sec                  
[  5]   1.00-2.00   sec  84.2 MBytes   706 Mbits/sec                  
[  5]   2.00-3.00   sec  84.1 MBytes   705 Mbits/sec                  
[  5]   3.00-4.00   sec  82.3 MBytes   690 Mbits/sec                  
[  5]   4.00-5.00   sec  84.0 MBytes   705 Mbits/sec                  
[  5]   5.00-6.00   sec  87.1 MBytes   730 Mbits/sec                  
[  5]   6.00-7.00   sec  84.0 MBytes   705 Mbits/sec                  
[  5]   7.00-8.00   sec  82.3 MBytes   690 Mbits/sec                  
[  5]   8.00-9.00   sec  67.4 MBytes   565 Mbits/sec                  
[  5]   9.00-10.00  sec  59.3 MBytes   498 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec   805 MBytes   675 Mbits/sec    1             sender
[  5]   0.00-10.00  sec   801 MBytes   672 Mbits/sec                  receiver

iperf Done.

 

Does anyone have an idea why the transfer speed is so different? What could I do to have the same experience for downloading from NAS as I do have when uploading?

 

 

[JorgeB]

Iperf confirms the issue is LAN related, probably the NIC since Realtek NICs driver support in Linux is a crapshoot, but could also be related to the switch, cable or the other PC.

[Kubernetes]

It seems the driver in unraid is from 2013. On another linux server with debian with same NIC the driver is from 2015.

How can I make a request to update the driver?

[JorgeB]

You can make a feature request.

[Ronan C]

Hello mate, i have a similar issue, i fix forcing my windows 10 realtek card to 1000mbps full duplex into the config's of the card, just try and let me know

[Kubernetes]

Hey Ronan, thank you for your reply and suggestion. Unfortunately it doesn't help to speedup the speed. 

[shovenose]

I have had all sorts of bizarre issues with a fairly new TP-Link managed switch and various Realtek gigabit NICs and one random mobo with a Marvell NIC (what a turd). Either the link would be unreliable or simply perform "wrong" or go down to 100Mbps randomly. No such issues with any other switch (including TP-Link unmanaged switches) nor the Realtek 2.5g NIC in my main desktop. I ended up resolving the problem by replacing the switch, although the issue did seem to be driver dependent as with some OS's the problem would never happen, while on some OS's it would be fine. Anyway, do me a favor, try a different ethernet cable and a different switch (or if directly connected to your router, throw an unmanaged switch in between). If that doesn't work, Intel NIC time they are cheap on eBay

[Kubernetes]

I am pretty sure that the problem is the driver used in unraid. When I boot debian linux with 'apt install firmware-realtek' the speed is 1Gbs in both directions. Howevery, I tried another cable (different manufacturer) without success. I don't have other switches than ubiquiti, so I cannot test with another switch. But I tried with cross over cableling and this also doesn't improve the speed with unraid.