Samba performance with 2 NICs does not scale as expected

David Collier-Brown davecb at
Mon May 17 13:07:22 GMT 1999

Zwika Moshkowzki wrote:
> 2 NICs on NT computer, 2 NICs on Samba server, 100BaseT network/
> (AlphaServer 1200, Digital UNIX, compiler = gcc, Samba version = 2.0.3).
> Copying 1(2) files, via SAMBA, yields 6.5(8.5) MBPS when 1(2) NICS participate.
> Copying 1(2) files, via FTP, yields 9.5(15) MBPS when 1(2) NICS participate.
> Any ideas?

	Well, you could just need to tune Samba somewhat: the
	current defaults now include socket options = TCP_NODELAY,
	so that's the first thing to try, followed by buffer sizes.

	However, this may also indicate a question of parallelization:
	when you do the test with two NICs, are you using a pair of
	FTP/Samba processes, one on each network, or are you issuing
	two FTP/Samba requests on a single process, and expecting 
	TCP to load-share between the two machines?  If so, you'll need
	to give us an idea about the configuration:
	0) are you using one or two ftp/samba clients for the test,
	   one on each subnet
	1) are the connections via different physical networks (normal)
	   or do you have two nics on one net by tricking one into thinking
           it's on a different subnet, but the same wire (unlikely,
	   but implied by your use of the singulare word "network")?
	2) what's your routing table look like?  Can IP see both paths
	   to the other host as having the same metric?

David Collier-Brown,  | Always do right. This will gratify some people
185 Ellerslie Ave.,   | and astonish the rest.        -- Mark Twain
Willowdale, Ontario   |
Work: (905) 477-0437 Home: (416) 223-8968 Email: davecb at

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