So, I guess I cannot speciy Normal or High redundancy because there is only one failure group .
I have 4 questions.
1.Given the above situation (all LUNs from same storage Frame) how many LUNs should be there in my OCR_VOTE disk group ?
Is recommeded to create 3 small luns (one in each array of storage if you have this option) and you can create a failgroup to each LUN. (the reason is multiplex Voting Disks to protect against logical, physical corruption or array issue)
Most of env have MPIO and RAID configured then about hardware (mean controller or disk failure) redundancy is solved at H/W level, but you can protect voting disk or ocr against Array Failure.
2. What redundancy shoud I configure for OCR_VOTE diskgroup ? Normal, High or External ?
External if you make sure that your hardware is highly protect against failure, RAID and MPIO is configured. But you will be unprotected against logical or physical corruption or array failure.
Normal you will be protect against physical or logical corruption and is recommended place one lun in different array on storage.
Mandatory use normal redundacy if you are using two or more storage system.
High if your cluster have more than 5 nodes and have two or more storage system is recommended use High rendundacy.
3.Is there any advantage in having an odd number of LUNs (3) for OCR_VOTE disk group in my case?
To place voting disk on a dg with normal redudancy you will need at least 3 Luns because Voting disk on a Normal redudancy requires 3 or more asmdisk.
3 Luns is not a Diskgroup requirement but a CSS requirement.
4. Is it good to have separate diskgroup for Voting disk and OCR ?
The only reason to separate it ( if you have RAID and MPIO at H/W level) is protect OCR against failure on Diskgroup.
If you have one Diskgroup (OCR_VOTE) configured properly, then this protect OCR in other Diskgroup is a plus.
p.s voting disk can be placed in one diskgroup. OCR can be placed in many diskgroup.
Recently I faced a customer lost 12 disks (failure) at the same time in a Storage DS8000, the Storage has over 100 physical disks.
Something that we considered impossible, but it can happens.