[Samba] Samba Variables and TCP/IP Throughput

AndyLiebman at aol.com AndyLiebman at aol.com
Wed Dec 17 13:23:18 GMT 2003

Thanks for the reply. Do you know (and if so, caan you tell me) what the 
relationship is between these Samba settings and Linux settings such as 
net.core.rmem_default (or _max), net.core.wmem_default (or _max), net.ipv4.tcp_rmem and 
net.ipv4.tcp_wmem.  Do the Samba options override the Linux socket options, or 
do they act as another layer of limits and buffers? 

Perhaps your TCP window is too small
You should try the following global settings:

    read size = 65535
    max xmit = 65535
    socket options = TCP_NODELAY SO_SNDBUF=65535 SO_RCVBUF=65535

Rgds Per

AndyLiebman at aol.com wrote:
> Hi,
> I am trying to optimize my gigabit network. I have two Intel 1000 MT Gigabit
> Server Adapters, which support Jumbo Frames -- as well as a Switch that
> supports Jumbo Frames. However, I am observing some strange behavior in my 
> transfers from Windows XP to Linux and I am wondering if it has anything to 
> with the way the Samba variables are set on my Linux box?
> The "strange behavior" is that when I set both NICs to use Jumbo Frames
> [MTU=9014 on the Windows side (includes IP headers) , 9000 on the Linux side
> (doesn't include the headers], I am getting about half the throughput that 
I get
> when I set both NICs to use the standard MTU of 1514/1500. I see the same
> behavior even if I take the switch out of the system and connect the 
Windows XP and
> Linux machines directly to each other (crossover cable not required for
> computer-to-computer connection with these NICs -- and by the way all of my 
> are CAT6).
> On the Linux side, I am using Samba 3.0.0 on Mandrake Linux 9.2 with all of
> Mandrake's current updates -- kernel = 2.4.22-21enterprisemdk. The Linux
> machine is a P4-3.06 Ghz with 1 GB of RAM -- running in hyperthreading mode.
> I am wondering if any of the Samba socket options settings like tcp_nodelay,
> so_sndbuf=8192 or so_rcvbuf=8192 are affecting my throughput -- particularly
> when I am using Jumbo Frames? And are there any other Samba settings that 
> be interacting in a negative way with my TCP/IP and NIC driver settings that
> are causing me to get lower throughput with Jumbo Frames instead of higher
> throughput (which is what I am told I should be getting).
> Any guidance would be appreciated. I have purchased "The Official Samba 3
> HOW-TO and Reference Guide" but it really isn't very helpful when it comes 
> understanding how to tune these options and how various socket options 
> interact with other network settings and hardware.
> Andy Liebman
> Resolute Films
> 119 Braintree Street, Suite 410
> Boston, MA 02134
> Tel: 617-782-0479
> Cell: 617-308-0488
> Fax: 617-782-1071
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