A primary objective of MHA is automating master failover and slave promotion within short (usually 10-30 seconds) downtime, without suffering from replication consistency problems, without spending money for lots of new servers, without performance penalty, without complexity (easy-to-install), and without changing existing deployments. MHA also provides a way for scheduled online master switch: changing currently running master to a new master safely, within a few seconds (normally 0.5-2 seconds) of downtime (blocking writes only).
