Tuning: 100mbit faster, gbit slower.

Tom Judge tom at tomjudge.com
Wed Apr 2 04:51:46 UTC 2008

Josh Paetzel wrote:
> This is on RELENG_6_3
> net.inet.tcp.sendspace=262144
> net.inet.tcp.recvspace=262144
> kern.ipc.maxsockbuf=1048576
> ifconfig em0 mtu 9014 (You'll need a switch that supports jumbo frames to do 
> this)

Daniel, you should note that all devices on your network also need to 
have the same MTU configured, and that Jumbo frames are only supported 
on gige connections so if you have any 100/10 devices you can not use 
jumbo frames.

> iperf shows wire traffic around 969 mbps and FTP runs at 110 Megs/sec
> scp/sftp appears to be cpu bound at 45 Megs/sec, and NFS with TCP mounts and 
> send/receive packets set to 16384 manages about 90 Megs/sec.

Hi Josh,

If you are running SCP/SFTP over your internal lan and are not worried 
about the security of the data in the session only the authentication 
then you man want to check out the HPN patches for openssh (I belive 
they are available as an option in the openssh port) which re-enable the 
cypher 'none'.  Also the latest patch set introduces multi threaded 
crypto so that ssh is not bound by the performance of a single cpu in 
multi cpu/core systems.

We run the HPN patches here (the older set with no multi threading 
support) and we can saturate gige with a single scp/sftp/ssh connection 
between two reasonably spec'd boxes (Our mtu is 8192 as this is more 
compatiable with most hardware [nics and switchs] most of the hardware 
wie have will only do 9000 byte jumbo frames).


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