Several things can be done to improve FTO failover time:
variable can save up to a few minutes in failover time. The variable
indicates how many times a MIRROR HUB should attempt to reconnect to its
peer HUB before assuming the primary HUB responsibilities. The default
for this variable is 2. Changing the value to 1 results in only one
reconnect attempt before assuming the primary HUB role.
Another variable that can be used to decrease failover time is the following:
This variable is
called the check interval. It dictates how often the HUBs will check to
see if its peer is still around when no data has been received for a
period of time. There are two parts to this check. If either fails then
the peer HUB is marked as disconnected. The default value is 120
default value, if no data has been received from the peer HUB for 60
seconds (1/2 the specified value), then a request called a "ping" is
sent to the peer HUB. If the ping request cannot successfully be sent,
then the peer is marked as disconnected.
If the ping
request is successfully sent, then the peer HUB is expected to return
the ping request within 2 check intervals. Assuming the default value,
this means that the request must be returned within 4 minutes. The peer
HUB is marked as disconnected if the request is not returned.
So using a check
interval of 30 can remove another 45 seconds from the failover time. I
do not recommend making the check interval much smaller than 30 as you
will increase the likelihood of falsely marking the peer HUB as
disconnected. The smaller check interval means there is less time for
the peer HUB to return the ping request, which can lead to false
disconnect state. Increase this value if you encounter false disconnect
One last thing that can be done to possibly improve failover time is to specify the following variables at both HUBs:
variables can reduce the number of interfaces that are checked when a
connection issue occurs between the two HUBs. These variables will
restrict the HUB to use only the interfaces specified in the
GLB_SITE.TXT file to communicate to the peer HUB.