DNFS with ASM over dNFS with file system - advantages and disadvantages.

Question

Hello Experts,
We are creating a 2-node RAC. There will be 3-4 DBs whose instances will be across these nodes.
For storage we have 2 options - dNFS with ASM and dNFS without ASM.
The advantages of ASM are well known --
1. Easier administration for DBA, as using this 'layer', we know the storage very well.
2. automatic re-balancing and dynamic reconfiguration.
3. Stripping and mirroring (though we are not using this option in our env, external redundancy is provided at storage level).
4. Less (or no) dependency on storage admin for DB file related tasks.
5. Oracle also recommends to use ASM rather than file system storage.
Advantages of DNFS(Direct Network File System) ---
1. Oracle bypasses the OS layer, directly connects to storage.
2. Better performance as user's data need not to be loaded in OS's kernel.
3. It load balances across multiple network interfaces in a similar fashion to how ASM operates in SAN environments.
Now if we combine these 2 options , how will be that configuration in terms of administration/manageability/performance/downtime in future in case of migration.
I have collected some points.
In favor of 'NOT' HAVING ASM--
1. ASM is an extra layer on top of storage so if using dNFS ,this layer should be removed as there are no performance benefits.
2. store the data in file system rather than ASM.
3. Stripping will be provided  at storage level (not very much sure about this).
4. External redundancy is being used at storage level so its better to remove ASM.
points for 'HAVING' ASM with dNFS --
1. If we remove ASM then DBA has no or very less control over storage. He can't even see how much is the free space left as physical level.
2. Stripping option is there to gain performance benefits
3. Multiplexing has benefits over mirroring when it comes to recovery.
(e.g, suppose a database is created with only 1 controlfile as external mirroring is in place at storage level , and another database is created with 2 copies (multiplexed within Oracle level), and an rm command was issued to remove that file then definitely there will be a time difference between restoring the file back.)
4. Now familiar and comfortable with ASM.
I have checked MOS also but could not come to any conclusion, Oracle says --
"Please also note that ASM is not required for using Direct NFS and NAS. ASM can be used if customers feel that ASM functionality is a value-add in their environment. " ------How to configure ASM on top of dNFS disks in 11gR2 (Doc ID 1570073.1)
Kindly advise which one I should go with. I would love to go with ASM but If this turned out to be a wrong design in future, I want to make sure it is corrected in the first place itself.
Regards,
Hemant

Answer 1

I agree, having ASM on NFS is going to give little benefit whilst adding complexity.  NAS will carrying out mirroring and stripping through hardware where as ASM using software.
I would recommend DNFS only if NFS performance isn't acceptable as DNFS introduce an additional layer with potential bugs!  When I first used DNFS in 11gR1, I came across lots of bugs and worked with Oracle Support to have them all resolved.  I recommend having read of this metalink note:
Required Diagnostic for Direct NFS Issues and Recommended Patches for 11.1.0.7 Version (Doc ID 840059.1)
Most of the fixes have been rolled into 11gR2 and I'm not sure what the state of play is on 12c.
Hope this helps
ZedDBA