SO_SNDBUFF & SO_RCVBUFF - Here are some practical recommendations

[David Lechnyr]

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Your mileage may vary, however I have found this to be a very reliable method of determining the optimal "socket options" values for SO_SNDBUFF and SO_RCVBUFF.  

1. Adjust your smb.conf to reflect:

	socket options = SO_SNDBUFF=4096 SO_RCVBUFF=4096 TCP_NODELAY IPTOS_LOWDELAY

2. Kill your smb/nmb processes, and restart samba.
3. From a workstation, download and install siSoft Sandra (http://www.3bsoftware.com/Downloads/sandra/sandra.html).
4. Map a drive to your samba server.  Disable any other TSR's/screensavers/antivirus/etc on your workstation.
5. Run ONLY the Drive Performance test on the mapped drive.  Record the Buffered/Sequential/Random Read/Write values (all six).
6. Repeat steps 1-6 again with the values 8192, 16384, 32768.  Anything greater will probably give marginal improvements, and less than 4096 (the defaults) will probably not work well at all.

Performance will fall off if you set the values too high, so this helps determine some optimal values.  Keep in mind that there are other options that will affect performance as well (e.g., disabling wide links, debugging), however this will help you to benchmark (with some accuracy) these "mystery" values.  Ironically (well, not really) you may find that the RCVBUFF and SNDBUFF values have different optimal values, esp. if your samba server is not on the same subnet and/or seperated by a packet filtering device.

Anyhow, I've gleamed lots from this discussion list over time so hopefully this is one way in which to contribute back ;-)
 
David Lechnyr, MCSE+I, CNE
Network Manager
Office of Human Resources
University of Oregon
PGPKey: http://hr.uoregon.edu/david-pgp.txt
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