Oracle CRS的心跳主要分为Disk和Network Heartbeat，不同种类的心跳超时会对RAC造成不同的影响。

Heartbeat Mechanisms

Disk Heartbeat ( Voting device ) – IOT
Network Heartbeat ( across the interconnect ) – misscount
Misscount – max time a heartbeat can be missed before entering into a cluster reconfig to evict a node
IOT – internal I/O timeout, in seconds where an I/O to the disk must complete
IOT = misscount [ during initial cluster formation time]
IOT = disktimeout [ all other times ] 

Hardware Storage timeout
Software Storage timeout
OCFS Heartbeat timeouts

disktimeout > max(O2CB_HEARTBEAT_THRESHOLD * 2, HW_STORAGE_TIMEOUT, SW_STORAGE_TIMEOUT)