Samba itself isn't necessarily to blame, I had a 550mb file I needed to transfer from my Kubuntu system (a fresh install of Kubuntu 10.10 Maverick less than a week old, but with all updates installed) to my Windows XP system and when I initially started the transfer the time was reported at about 2 hours, even after letting it go for a few seconds it still was reported at around 1 hour and 50 seconds. I've done transfers around this size from Windows to Windows systems and usually it takes around 10 minutes or so (depending on whether I'm surfing the web at the same time or not), so I knew something was really screwed up here. I had been originally using the onboard VIA 6103 NIC ,which was giving me excellent torrent download results and excellent web download results as well, but I decided to try some of the other PCI bus NIC cards I had lying around. Below are the results I obtained with each card WITHOUT modifying my samba configuration at all.
1) Linksys LNE-100TX Ver. 5.1 - Transfer reported approximate time at about the same as VIA 6103
2) D-Link DFE-530TX+ Rev-F1 - Again almost the exact same results as the VIA 6103
3) Unbranded card with MX98713FC Chipset - Caused system to hang a few seconds into transfer
4) 3Com 3C905B (tried and true card supported by pretty much every PC operating system in the world) - knocked about 10 seconds off the reported transfer rate.
5) Unbranded RTL8139D Chipset based card - Apparently not supported by Kubuntu for some reason or bad card.
6) Farallon RTL8139C Chipset based card - Transfer time dropped to about 7 Minutes instead of around 2 hours!!!!
AFIK all of these cards are 10/100 cards, the 3Com, Linksys, D-Link and MX98713FC based card are definitely supposed to be capable of 100mbs connections, as is the Farallon card (indicated by the presence of a 100mbs indicator LED on some of them).
To me this indicates a pretty serious problem with the default configuration of a number of the kernel modules/drivers/etc.. that are used to support some of the cards above, it's pretty sad when a generic cheapo RTL8139C based card can blow some of those other major brand name cards out of the water the way it did.
The specs of the system I did this on are as follows:
CPU: AMD Athlon XP 2400+ w/266mhz FSB
MB: DFI KT-600AL
RAM: 1.5Gb PC3200 (DDR-400) running at 400mhz
Video: nVidia MX-4000 PCI card w/128mb memory
Audio: Onboard VIA 8237 integrated audio
HD: 160Gb Western Digital IDE (PATA) hard drive UDMA5
DVD: Samsung SH-S222A 22X DVD burner
I admit this was by no means a scientifically conducted test but the results do seem to speak for themselves indicating a problem with the default configuration of the various kernel modules.