Oracle Database Scan Order and Multipath Configuration

Hi,
We had some issues on our Oracle Database Servers and all the issues were related to storage connectivity at different layers.

First Question)
Is there any difference between the below Oracle Scan Order configuration when there is no SCSI disk (Single Path) for ASM:
ORACLEASM_SCANORDER="dm sd"
Or
ORACLEASM_SCANORDER="dm"
ORACLEASM_SCANEXCLUDE="sd"

I think that there is no difference between the above configurations and also exclusion has no effect on DM-Multipath. Also I think that the first configuration doesn't help during path failure. Am I right?

https://access.redhat.com/solutions/88573

Second Question)
Can I have your advise about reducing path failure detection time and recommended configurations for EMC Unity?
Here is Multipath Helper result for DGC devices:

Cause of ISL configuration, we have more than 16 paths per path group for a disk. When one of switches have failed, some of database nodes were crashed but there was enough redundancy to preventing service downtime.
I have read this: https://access.redhat.com/solutions/137073
But I want to have lowest time.

BR
Davoud