How much latency is there for planned and unplanned failover?

Planned failover is the one in which the administrator of SAP HANA shut down the system for some reason pertaining to maintenance, patching data services, etc.

Unplanned failover is very abrupt in nature and is caused by software or hardware failure, natural or man-made disasters.

What i feel is that there are following steps involved in the failover and these make up for the total latency:

1) Identifying that the system failure has occurred

2) trying to bring back the system to its normal stage with minimum efforts

Under the case of planned failover we can notify the system about the reason of the downtime, which in turn eliminates system's effort to recognize the problem. So we are eliminating this latency. Now the system have just to take the appropriate step to complete failover process.

In case of unplanned failover the system itself to recognize the reason for the downtime and this adds up to identifying the cause latency. After identifying the cause the system takes in the appropriate step to complete failover process.

I believe what i am assuming is correct. And if i am correct can anyone help me evaluate the actual latency for planned and unplanned failover? Feel free to add onto this discussion