Why is Samba Access from Windows So Slow?

Try configuring your server without setting SO_RCVBUF and SO_SNDBUF. Ie:

socket options = TCP_NODELAY

and nothing else. Or comment out socket options entirely and use Samba's default.

I had a similar problem with Ubuntu 12.04 and a Mac client on gigabit ethernet. Reading a file was getting about 100kbytes/second, or 300 times too slow. In Ubuntu 11.10 I was setting both buffers to 8192 as you tried. But when I upgraded to 12.04 I found I had to remove that setting to get performance back to where it should be (about 30mbytes/second, the disk speed).

Another solution I've seen suggested is to set max protocol = NT1. I tried that first and it didn't help me.