[Pacemaker] MySQL/PostgreSQL HA cluster with Pacemaker

[Andrew]

Hi all.
I try to build 1+1 MySQL HA cluster, and currently I'm looking on 
Percona replication manager; other variant - to write own OCF for 
semi-synchronous master-slave replication. Also I want to run here 
PostgreSQL HA DB.
So I have some questions:
1) How pacemaker decides what node should be master, when both nodes 
booting after, for ex., power failure? First running node will become a 
master, or Pacemaker can wait some time till node, that was a master 
before crash, will be running?
2) Is there a solution that may be better for data integrity?
3) What solutions are present for Postgres excluding classical DRBD 
solution?