Before you start, you need to know:
- Read/Write Ratio
- Throughput in IOPS

Spindle count = [(RR x TT) + (WP x WR x TT)] / RoT

Where:
RR is read ratio
WR is write ratio (RR+WR=100%)
WP is write penalty (RAID1/0=2; RAID5=4; RAID6=6)
RoT is RoT drive throughput (15Krpm=180; 10Krpm=140; NL-SAS=100)
TT is total throughput in IOPS

Remember to roundup the spindle count to the nearest RAID size.

Recommended RAID sizes are:

RAID5: 5 drives (4+1) or 9 drives (8+1)

RAID6: 8 drives (6+2) or 16 drives (14+2)

engkong,

Please consider moving this question to the proper forum for maximum visibility.  Questions written to the users' own "Discussions" space don't get the same amount of attention and questions can go unanswered for a long time (if at all).  You can do so by selecting "Move" under ACTIONS along the right.  Then search for and select: "Unified Storage" which would be the most relevant for this as it can related to both CLARiiON and VNX (despite you calling out specifically NL-SAS).  There is also a recent post demonstrating the steps to do the same:

EMC Community Network Frequently Asked Questions

I see that you had found the answer on your own and have written up a nice summary of the things to consider.  Let's definitely get this posted to the proper forum for the benefit of others that may be looking for the same.  Also, consider marking your question as "Answered" as that helps in the search.  In addition, I believe you will get points even for marking your own question as such.