Need to choose ASM performance for production database We have a 1.5 TB of data (nonasm) and we plan to move into ASM by choose normal redundancy. 

Normal Redundancy ==> Two Way Mirroring , So we need 3TB data storage for 1.5TB data including mirroring(SAN disk).

Please clarify below:

A) If we choose single RAW disk 3TB.

How many disk group we can split?

either each 500gb into 6 parts? (1 disk group) 

This will be efficient for asm operation? 

If the failure group we need to specify mandatory?

In our case, we have a single 3TB disk for storage, so no need to specify failure group right?

From blogs,

((For small numbers of disks (&lt;20) it is usually best to use the default Failure Group creation that puts every disk in its own Failure Group))

so It can take by default itself. So no need to specify right?

B) If we have separate two disks each 1.5 TB

How many disk group we can split, either each 500gb into 3 parts? 
(Total 2 disk group a and b)

If the failure group we need to specify mandatory? 

Shall we specify manually failure group of A disk group is B and failure group of B is A? 

Its a better performance? 

If you cause a failure group specification it causes a spindle failure?

Either A or B case, which one is better performance approach for I/O operation in ASM?
ASM is not magic.

Each disk has a maximum number of IOPS it can support.  Each disk has a maximum throughput.  The more spindles (HDDs) you have, the more I/O you can get.  If one disk decides to take a permanent vacation and you don't have data on another disk.... I really hope you have viable tested backups.

From my tests, partitioning a single HDD into multiple LUNs and then using those LUNs for ASM will have a negative effect (albeit, ~-1%).

If you want performance, you will buy 6+ 500GB HDD (or SSD).  Each disk will have 1 LUN - the whole thing.  ASM will take care of the stripe and mirror.