Article Q2156
outlines how to configure redundant IO Servers to the same serial
IO Device, however many control systems also utilise redundant IO
devices and connect to them via Ethernet. For redundant servers
connecting to redundant Modnet devices on a single network an
illustrative configuration follows, extending on that suggested in
article Q2156 and referring to the Driver
Help for Modnet devices. This assumes you have two CitectSCADA
machines - ‘CitectP’ which runs ‘IOserverP’ (primary), and
‘CitectS’ which runs ‘IOserverS’ (standby) - and real IO device
‘Device1’ (primary) at 192.168.0.11 and real IO device ‘Device2’
(standby) at 192.168.0.12.
| |
CitectP
|
CitectS
|
| IO Servers:
|
|
|
|
|
| Name: |
IOserverP |
|
IOserverS |
|
| Boards
|
|
|
|
|
| Server Name: |
IOserverP |
|
IOserverS |
|
| Board Name: |
IOserverP_Board1 |
|
IOserverS_Board1 |
|
| Board Type: |
TCPIP |
|
TCPIP |
|
| Address: |
0 |
|
0 |
|
| Ports:
|
|
|
|
|
| Server Name: |
IOserverP |
IOserverP |
IOserverS |
IOserverS |
| Port Name: |
Board1_Port1P |
Board1_Port2P |
Board1_Port1S |
Board1_Port2S |
| Board Name: |
IOserverP_Board1 |
IOserverP_Board1 |
IOserverS_Board1 |
IOserverS_Board1 |
| Port Number: |
1 |
2 |
1 |
2 |
| Special Options: |
-I192.168.0.11 |
-I192.168.0.12 |
-I192.168.0.11 |
-I192.168.0.12 |
| IO Devices:
|
|
|
|
|
| Server Name: |
IOserverP |
IOserverP |
IOserverS |
IOserverS |
| Name: |
Device1P |
Device2P |
Device1S |
Device2S |
| Number: |
1 |
1 |
1 |
1 |
| Address: |
|
|
|
|
| Protocol: |
MODNET |
MODNET |
MODNET |
MODNET |
| Port Name: |
Board1_Port1P |
Board1_Port2P |
Board1_Port1S |
Board1_Port2S |
| Startup Mode: |
Primary |
Standby |
Standby |
Standby |
As you can see, you will need to configure in your project two IO
Servers, each with one Board, which is in turn referred to by two
Ports and their associated IO Devices. Thus, you have four Ports
and four IO Devices configured. Note that the IO Device Address
field is left blank for Modnet devices. Note also that only one of
these IO Devices has Startup Mode ‘Primary’ and the other three
have Startup Mode 'Standby’, however the IO Device Number is the
same for all.
The IO Device Number is crucial since in the variable tag
configuration you specify the device that is associated with that
tag by its IO Device Name – always select the IO Device which has a
Startup Mode of 'Primary', in this case ‘Device1P’. CitectSCADA
knows that this tag is also associated with the standby devices
(‘Device2P’, ‘Device1S’ and ‘Device2S’) because these devices share
a common IO Device Number with ‘Device1P’. This means that even
though the IO Device is actually a pair of real devices, which are
in turn configured as four IO Devices in CitectSCADA, you only need
to define each variable tag once in your project.
The order in which these devices appear in the units.dbf file will
determine the order in which the standby devices are used in the
event of a failure. It is recommended that the units.dbf file in
your project folder is opened with a third party application such
as Excel and you ensure the IO Devices appear in this order:
Device1P
Device2P
Device1S
Device2S
(As always, do not modify the column widths of any dbf file opened
in Excel, and always close the file using the ‘Save/Close DBF’
option in the right-click menu enabled by running the SAVE_DBF.xls
macro found in the Bin directory.)
After completing this configuration and restoring the project to
the two machines, ensure you run the Computer Setup Wizard on each
machine and select the correct IO Server in each case.
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