[stunnel-users] running concurrent stunnel instances

Tue Apr 10 10:12:46 CEST 2007

John Taylor wrote:
> Even though I have a gigabit connection between the two servers, I
> am only seeing 5-6% network utilization.

What about CPU utilization?  You can check it with "Task Manager" tool.

> I would like to see about increasing my throughput with stunnel encryption
> running.  I don't expect it to be as fast as running without stunnel,
> but I still think I should be able to do better than 5-6% throughput.

I agree.

> Thus,
> the multiple rsync.exe processes get the advantage of running on top of
> multiple cores.  This is not the case with stunnel.exe.  It only uses 1
> process, but 8 threads.

You're wrong.  Stunnel threads are distributed among your CPUs even on
your Win 2003 Server so-called operating system.
http://msdn2.microsoft.com/en-us/library/ms681917.aspx

> I am hoping that multiple stunnel.exe instances
> will fix the bottleneck because each stunnel.exe process could then be
> running on it's own core.

There will be no improvement.

>    ciphers = AES128-SHA

Try ciphers=RC4-MD5 for best performance.
See http://stunnel.mirt.net/perf.html for details of what you can expect.

If you can send me your stunnel logs (generated with "output" option) I'll
possibly be able to give you some more performance hints for your system.

> Any help would be greatly appreciated.

I fully agree.  Enter http://stunnel.mirt.net/, click "DONATE" and follow
the instructions to help.  8-)

Best regards,
    Mike