| Citect Trend Server redundancy operates in
a Primary/Standby configuration. When both Trend Servers are
running, the Trends are processed on both servers in parallel, and
both written to disk. Because of this, each server must write to
its own disk or private area on the file server. The Trend data is
synchronised between the Primary and Standby servers in the
following way: On startup, the Trend server will try to connect to
the other Trend server. If it can connect, it will then transfer
all the trend data from the last time it was shutdown to the
current time.
You can only configure two Trend servers in a Citect project,
the Primary server and Standby server. Citect Clients either talk
to the Primary or Standby Trend server. On startup, they will try
to talk to the Primary. If the Primary is not running, they will
try the Standby. If the Primary comes back online, any Clients
talking to the Standby will stay talking to the Standby server. (It
does not matter which Trend server the clients talk to as they both
contain the same data.) Allowing Clients to attach to either server
will help balance the load generated by each client on the
server. |
