I can't really identify a common problem. Things I've seen include:
* After a complete, planned shutdown, neither server is happy to start until it sees the other one online. In the end, neither ends up booting.
* A failover occurs, at which point you find out the hard way there is state being stored in a non-replicate file. I've seen this with several different Asterisk HA solutions in particular.
* A failover occurs, and non-database aware storage snapshots leave the redundant server with a non-mountable mirror of the database.
* After a complete, planned shutdown, neither server is happy to start until it sees the other one online. In the end, neither ends up booting. * A failover occurs, at which point you find out the hard way there is state being stored in a non-replicate file. I've seen this with several different Asterisk HA solutions in particular. * A failover occurs, and non-database aware storage snapshots leave the redundant server with a non-mountable mirror of the database.