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DSM6: Slow DL speed when using hostname, fast when using IP

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So I am playing around with DSM 6 (Update 6, jun's loader v1.01) on my ASRock J3455M, Realtek RTL8111E NIC.

 

I noticed that when downloading a file from DSM via SMB, there is a HUGE drawback in speed when I access it via its hostname (like \\mydiskstation). Download speed ranges from <1 MB/s to ~2.5 MB/s depending on the client I run the test on.

 

When I use the IP address instead (like \\192.168.1.10) everything is fine and I download at full GBit speed (up to 110 MB/s).

 

This could be reproduced on two different laptops (Lenovo X201 and R61) and three operating systems (Windows 10, Windows 7 and Ubuntu 16.04).

It could NOT be reproduced when uploading a file. Upload speed varies between 70 and 110 MB/s regardless the way I access the machine.

 

I have a Zyxel NAS on the same network which happily provides its full download speed of ~45-50 MB/s both via hostname and IP address.

 

All additional packages that I had installed before have been stopped and QuickConnect has been disabled.

The network settings are all pretty default, fiddling around with the SMB protocol didn't help. Static IP vs. DHCP didn't make a difference either.

 

I see the same scenario when downloading a file via HTTP (web interface) or SFTP (ssh).

Using the host name: very, very low speeds (< 1 MB/s using HTTP, even less using SFTP).

Using the IP address: 45 MB/s using HTTP, >10 MB/s using SFTP (which seems rather slow too, but SFTP is not a use case for me at the moment, so I don't really care).

 

So I assume it's safe to say that this has nothing to do with the SMB protocol but seems to be a problem somewhere further down the network stack.

 

When I googled around for that issue, I found several forum posts even on the official Synology forum by people who seem to have similar problems with their genuine Synology boxes. Although they usually just complain about their download being slow.

 

Any help would be appreciated! :idea:

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Some more info:

 

Driver seems to be r8168 in version 8.043.01-NAPI. According to the Realtek website, this is (almost) the most recent version (8.043.02 currently being available for download).

root@DiskStation:~# dmesg | grep 'Ethernet'
[   30.763611] Intel(R) Gigabit Ethernet Network Driver - version 5.3.5.4
[   30.815623] i40e: Intel(R) Ethernet Connection XL710 Network Driver - version 1.3.47
[   31.651453] bnx2x: QLogic 5771x/578xx 10/20-Gigabit Ethernet Driver bnx2x 1.714.0 ($DateTime: 2016/08/25 21:13:29 $)
[   31.992124] pch_gbe: EG20T PCH Gigabit Ethernet Driver - version 1.01
[   32.012556] QLogic 1/10 GbE Converged/Intelligent Ethernet Driver v5.2.42
[   32.630113] r8168 Gigabit Ethernet driver 8.043.01-NAPI loaded

 

root@DiskStation:~# uname -a
Linux DiskStation 3.10.77 #8451 SMP Wed Aug 17 05:12:41 CST 2016 x86_64 GNU/Linux synology_bromolow_3615xs

 

root@DiskStation:~# ethtool -i eth0
driver: r8168
version: 8.043.01-NAPI
firmware-version:
bus-info: 0000:01:00.0
supports-statistics: yes
supports-test: no
supports-eeprom-access: no
supports-register-dump: yes
supports-priv-flags: no

 

I will try to get my hands on a NIC with Intel chipset and see if that changes anything.

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I now got a par of HP NC110T NICs from eBay (in used condition at just 5$ each). These use the Intel 82572GI controller and are supported by the e1000e driver:

 

root@DiskStation:~# ethtool -i eth0
driver: e1000e
version: 3.3.5-NAPI
firmware-version: 5.11-10
bus-info: 0000:02:00.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: no

 

Using this NIC, the slow download rates are gone. Everything works at full GBit speed now, regardless the way I access the machine.

 

If you google around for RTL8111E and r8168, you will find A LOT of issues people are experiencing with this chip and this driver on Linux. Although most of the issues should have been fixed in the driver by now and it is said to be performing quite well, this doesn't seem to be quite true for my setup.

I will just disable the onboard Realtek chip and use the Intel card(s).

 

So my recommendation by now would be: If you run into trouble with the RTL8111E, this is most certainly an issue with the driver. Don't waste your time trying to fix it - go and grab an Intel based NIC off eBay instead.

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