Overview – Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) User Manual

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Brocade Virtual ADX Server Load Balancing Guide

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Miscellaneous health check settings

Overview

The Brocade Virtual ADX uses the server slow-start mechanism to adjust the maximum number of
connections that can be established for a real server that has just gone online. The Brocade Virtual
ADX begins with a connection limit that is lower than the maximum configured value (which is one
million by default) and gradually increases this connection limit until the maximum configured
value is reached.

The server slow-start mechanism is especially useful when least connections is the distribution
predictor. Without the server slow-start mechanism, a server that is just brought online could
receive all the new connections in a flurry, which could bring the server down. Many servers cannot
handle more than 2,000 new connections per second.

NOTE

The server slow-start mechanism is always applied to all real servers when they are brought online.
Unlike the slow-start mechanism for individual ports, described in the next section, the server
slow-start mechanism is not configurable.

The two graphs in

Figure 26

illustrate how the server slow-start mechanism ramps up the

connections for a real server during the 30-second slow-start period. The graph on the left shows
the rate at which the number of connections increases over the slow-start period. The graph on the
right shows how the maximum number of connections that the Brocade Virtual ADX allows for the
real server increases over the slow-start period.

FIGURE 26

Slow-start mechanism for a real server

The graph on the left shows the rate at which the Brocade Virtual ADX allows connections for a
given real server, as follows:

•

From the time the real server is brought online from 10 seconds to 20 seconds, the Brocade
Virtual ADX allows a max-connection rate of 10 times the elapsed time. During this period, the
Brocade Virtual ADX increases up to 10 new connections every second on the real server.