6
System overview
This section explains the basic principles behind a redundant system.
Primary and Backup controllers
The Primary system controller is the main system controller and during normal operation will perform the
operational functionality. Once designated as the Primary during configuration, the system controller will
always be the Primary within the system until the configuration changes.
The Backup system controller is also designated during configuration and is always the Backup system
controller in the redundancy system. In normal operation the Backup will operate in Standby mode
whereby it is continuously synchronised with the Primary and monitors the Primary’s health. In the event
of a Failover, the Backup will assume control by Deactivating the Primary and becoming Active.
Note that the synchronisation is from Primary to the Backup. Once the Backup becomes Active then the
Primary will not remain synchronised with the Backup. Restoring the Primary to be the Active system
controller is a Manual operation, at this point the Backup will return to Standby mode and synchronise
itself with the Primary again.
Active system controller
The Active status denotes the system controller that is currently actively controlling the system. Either
the Primary or Backup can be active, only one can be Active at any time. Note the Primary is always the
Primary and the Backup is always the Backup, it is the Active state that determines which unit is currently
in control.
Writing configurations
When using the TallyMan configuration software, unless connected to the system, all configuration is
performed offline. Configuration files are always written to the Primary system controller using the NIC1
IP address as defined in the configuration. Upon receiving a new configuration, the Primary will load the
configuration file and reconfigure itself accordingly to establish which mode to run in and whether it is
designated as Primary or Backup. Once it has determined it is the Primary and finished loading, it will
then automatically write the configuration to the Backup unit, which will then go through the same
process to determine its mode and function.
Connecting to the system
Each system controller has two Ethernet NICs and can thus support two separate networks. Writing
configurations and connecting to the system is performed using the static IP address assigned to these
NICs. You must use NIC1 to connect to the system.
Within a redundancy system there is also a virtual IP address assigned to each NIC. This is used for
communications to equipment outside of the redundancy ‘bubble’.
Ethernet
Each TM1-Mk3+ unit can support two separate networks to perform control functions. For a redundant
system, both units must use the same subnets for each NIC. For example, if NIC 1 of the Primary TM1-
Mk3+ is on the subnet 192.168.10.XXX then the Backup unit’s NIC 1 must also use the subnet
192.168.10.XXX. See IP Address and VIP assignment example.
Each NIC port also hosts a Virtual IP address (which must be on the same subnet as the permanent IP
address) that is defined in the TallyMan configuration software (as described below). This is different to
the static IP addresses that are configured via the front panel of each unit and is used as part of the
redundancy operations.
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