Socket options
The next thing to look at are the socket options configuration options. These are really host system tuning options, but they're set on a per-connection basis, and can be reset by Samba on the sockets it employs by adding socket options = option to the [global] section of your smb.conf file. Not all of these options are supported by all vendors; check your vendor's manual pages on setsockopt (1) or socket (5) for details.
example)
socket options = TCP_NODELAY SO_RCVBUF=32768 SO_SNDBUF=32768
The main options are:
TCP_NODELAY
Have the server send as many packets as necessary to keep delay low. This is used on telnet connections to give good response time, and is used - somewhat counter-intuitively - to get good speed even when doing small requests or when acknowledgments are delayed (as seems to occur with Microsoft TCP/IP). This is worth a 30-50 percent speedup by itself. Incidentally, in Samba 2.0.4, socket options = TCP_NODELAY became the default value for that option.
IPTOS_LOWDELAY
This is another option that trades off throughput for lower delay, but which affects routers and other systems, not the server. All the IPTOS options are new; they're not supported by all operating systems and routers. If they are supported, set IPTOS_LOWDELAY whenever you set TCP_NODELAY.
SO_SNDBUF and SO_RCVBUF
The send and receive buffers can often be the reset to a value higher than that of the operating system. This yields a marginal increase of speed (until it reaches a point of diminishing returns).
SO_KEEPALIVE
This initiates a periodic (four-hour) check to see if the client has disappeared. Expired connections are addressed somewhat better with Samba's keepalive and dead time options. All three eventually arrange to close dead connections, returning unused memory and process-table entries to the operating system.
There are several other socket options you might look at, (e.g., SO_SNDLOWAT), but they vary in availability from vendor to vendor. You probably want to look at TCP/IP Illustrated if you're interested in exploring more of these options for performance tuning with Samba.
