NLB Behavior

[Jonty Goldin]

I have been running some performance tests on a web-farm
with two hosts, to determine if NLB is working as
expected. I have noticed some unusual behaviour during
these tests.

During the test I remove one of the the hosts, observe the
load redistributing, then reconnect the host, and observe
the load balancing. I monitor the counter: Web Service >
Current Connections in Performance Monitor, for each of
the hosts in the web-farm cluster.

When I disconnect the host, the load on the connected host
increases (after a period of convergence) as expected.
When I reconnect the removed host, the load on the
existing host drops to it's original load, as expected,
but it takes about 2 - 3 minutes for the reconnected host
to take on any of the load.

Does anyone know why there is such a long delay? I have
played around with session timeouts in the ASP
configuration files (web.config), to no avail.

Any explinations would be welcome.

Thanks in Advance.
Jonty

 

[Curtis Koenig [MSFT]]

Hi Jonty,
For the most part this has to do with the TCP/IP sessions resetting after a
given time and not with the application that is being load balanced. You
should consider this normal behavior as it takes time for the TCP session
to end and a new request to be sent that can then be hosted by the
restarted node.
--
Curtis Koenig
Support Engineer
Product Support Service Security Team
MCSE, MCSES, CISSP

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