[Samba] No increased throughput with SMB Multichannel and two NICs

Daniel Vogelbacher daniel at vogelbacher.name
Tue Sep 6 13:56:14 UTC 2016

Am 2016-09-06 10:41, schrieb Anoop C S via samba:
> On Sun, 2016-09-04 at 11:42 +0200, Daniel Vogelbacher via samba wrote:
>> Hello,
>> I'm running Samba 4.4.5 with enabled SMB Multichannel. The Linux
>> server
>> has two 1GBit/s NICs and for testing purposes I've shared a tmpfs
>> mountpoint with 2GiB and ~2GiB large test-file.
>> My Windows 10 host has one dual-port 1GBit/s NIC, and if both
>> interfaces
>> are enabled, Get-SmbMultichannelConnection lists active multichannel
>> connections to my Linux SMB server.
>> If I disable one NIC on Windows, the other NIC is used with ~1GBit/s
>> when transferring the test-file from Linux to Windows.
>> If I enable both NICs, instead of 2x1Gbit/s I only get ~500MBit/s per
>> interface (but both interfaces are used).
>> So instead of doubling the throughput, traffic is split up between
>> two
>> interface half by half.
> This is mostly a Windows client-controlled behavior. Refer to the
> following reply for a thread on similar subject for more details. 
> https://lists.samba.org/archive/samba/2016-August/201841.html

[...]AFAIK, the windows client only puts traffic on interfaces of same
speed and quality simultaneouslt[...]

I interpret this as "with two identical NIC-speeds at server-side and 
client-side it should result in double throughput".
On both hosts I've 2x1GBit/s NICs and Windows uses both(!) NICs (but not 
at full speed when multichannel is enabled). So I don't think my problem 
is related to this thread, beacuse if it is, Windows would choose only 
one NIC.

>> Is it possible to change this behaviour?
>> Hardware infos on Linux:
>> 07:00.0 Ethernet controller: Intel Corporation I210 Gigabit Network
>> Connection (rev 03)
>> 08:00.0 Ethernet controller: Intel Corporation I210 Gigabit Network
>> Connection (rev 03)
>> # uname -a
>> Linux mz4 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt25-2+deb8u3
>> (2016-07-02) x86_64 GNU/Linux
>> /# /usr/local/samba/sbin/smbd --version
>> Version 4.4.5
>> Hardware infos on Windows 10:
>> Intel PRO/1000 PT Dual Port Server Adapter
>> Regards,
>> Daniel Vogelbacher

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