Chapter 2
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group receive broadcasts of metrics data from the
big3d
agents. All
members of the sync group also receive broadcasts of updated configuration
settings from the 3-DNS Controller that has the latest configuration changes.
When you define the sync group, you select the sync group members from
the list of 3-DNS Controllers you have already defined. The sync group lists
the 3-DNS Controllers in the order in which you selected them. The first
3-DNS Controller in the list becomes the principal 3-DNS Controller. The
remaining 3-DNS Controllers in the list become receivers. If the principal
3-DNS Controller becomes disabled, the next 3-DNS Controller in the list
becomes the principal 3-DNS Controller until the original principal 3-DNS
Controller comes back online.
Understanding how a sync group works
The sync group feature synchronizes individual configuration files, such as
wideip.conf
, and other files that store system settings. You have the option
of adding files to the synchronization list.
The 3-DNS Controllers in a sync group operate as peer servers. At set
intervals, the
syncd
utility compares the time stamps of the configuration
files earmarked for synchronization on all of the 3-DNS Controllers. If the
time stamp on a specific file differs between 3-DNS Controllers, the 3-DNS
Controller with the latest file broadcasts the file to all of the other 3-DNS
Controllers in the group.
Understanding how the time tolerance variable affects a sync group
The time tolerance variable is a global variable that defines the number of
seconds that the time setting on one 3-DNS Controller can be ahead or
behind the time setting on another 3-DNS Controller. If the difference
between the times on the systems is greater than the time tolerance, the time
setting on the 3-DNS Controller running behind is reset to match the 3-DNS
Controller with the most recent time. For example, if the time tolerance is 5
seconds, and one 3-DNS Controller is running 10 seconds ahead of the
other, the 3-DNS Controller running behind has its time reset to match the
one running 10 seconds ahead. If the second system was running only 2
seconds ahead of the other, the time settings would remain unchanged. The
values are 0, 5, and higher (values of 1-4 are automatically set to 5, and 0
turns off time synchronization). The default setting is
10
seconds.
The time setting on 3-DNS Controllers is important because a 3-DNS
Controller compares time stamps on files when deciding whether to
synchronize files with other 3-DNS Controllers in the sync group.
Setting up communications on a 3-DNS Controller
There are three different communication issues that you need to resolve
when you set up communication between the 3-DNS Controllers running in
your network.
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