Session/Connection Management during a Failover event in a HA Peer
Can any one explain during a failover event when secondary unit takes lead as primary how it handles sessions and on going connections,is there any stateful awareness managed at any layer as switchover is a matter of few seconds as i ahve aobservered even connection/session mirroring is not enabled . or sessions replicated to HA peer too ?
This is a good question. It all really depends on the application.
By default we do not mirror any connection information. In short, afte a failover, the standby device (now active) just starts ARPing for the destination IP and it will process connection accordingly.
Most modern web application, just open a new connection to the new active device and continue as needed. So that may be why your seeing everything work pretty well during a failover.
As for timing, this depends on the failure. If it's a user induced failover, it should be pretty seamless, possibly a second or two pause. But if this is more of a network failure and the devices don't have a direct failover link, it could take up to 90 seconds. Most of the time it's about 10-30 seconds.