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

Daniel Vogelbacher daniel at vogelbacher.name
Tue Sep 6 23:10:15 UTC 2016

On 07.09.2016 00:18, Jeremy Allison via samba wrote:
> On Tue, Sep 06, 2016 at 11:53:04PM +0200, Daniel Vogelbacher via samba wrote:
>>> Delete all the crap above first :-).
>>> Then start trying to copy locally to the tmpfs share to see what
>>> the max local copy speed it.
>> Now I have:
>> server multi channel support = yes
>> vfs objects = aio_pthread,recycle
>> aio read size = 1
>> aio write size = 1
>> strict locking = No
>> But read (linux->windows) transfer rate is now again 1GBit/s instead of
>> 2GBit/s?!
> OK, very strange. But at least you can now
> add in the things I told you to remove one
> by one to see which one I was wrong about :-).
> Don't keep adding, add one - then remove and
> add another until we discover which makes
> the difference (if it's indeed one, which
> I'm guessing) !

Okay, just after dozens of windows reboots, it works now for read/write
in both directions without changing the smb config.

One small issue: for small files <5GiB the whole transfer is done at
~210MiB/s. For larger files, after a few seconds (>10sec) the throughput
is reduced to ~70MiB/s. Source and Destination is a tmpfs/ramdisk, so
this should only related to networking.
There are plenty of tutorials around "how to tune your fileserver" with
net.core.rmem_max & others. Can you recommend any values for these
sysctls or have an idea why the speed is reduced?

Daniel Vogelbacher

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