RE: ASM vs. dNFS?

From: Hameed, Amir <>
Date: Wed, 24 Feb 2016 02:12:34 +0000
Message-ID: <>

In our case, there is no router between the switches, servers or the EMC Data Movers. Jumbo frames are configured end-to-end. Cisco, EMC and Oracle’s network engineers (These are M5000 servers) looked at the configurations end-to-end multiple times but could not find anything. We also reached out to Kevin Closson and he helped us run a lot of diagnostic tests which clearly showed that the throughout was not what it should be but no one was able to point out the root cause. The issue was escalated to higher ups within Oracle and Oracle’s dNFS development team gave us a beta patch to see if by increasing the dNFS buffer size would alleviate the problem but that patch had even more adverse impact on the performance. This diagnostics exercise lasted for months but no smoking gun was found. Now, it is entirely possible that the bottleneck is somewhere in our infrastructure but if all the vendors are not able to determine what is causing the slowness then I would think that due to the umpteen layers involved in the NFS architecture, it is quite a complicated beast. We also had two other Oracle ERP systems configured with dNFS and had the similar issue. Those systems were running on RHL and UCS and the moment we moved them back to FC, their performance improved considerably and the customers stopped complaining.

From: kyle Hailey [] Sent: Tuesday, February 23, 2016 7:44 PM To: Hameed, Amir
Cc:; Ruel, Chris; Subject: Re: ASM vs. dNFS?

I thought the FC vs NFS debate was dead back when Kevin Closson jokingly posted "real men only use FC<>" almost a decade ago. A recent example is Top 7 Reasons FC is doomed<>

NFS is the future, has larger bandwidth than FC, market is growing faster than FC, cheaper, easier, more flexible, cloud ready and improving faster than FC.

In my benchmarking, FC and NFS, throughput and latency are on par given similar speed NICs and HBAs and properly setup network fabric.

Simple issues like having routers on the NFS path can kill performance.


NFS has a longer code path than FC and with it comes some extra latency but usually not that much. In my tests one could push 8K over 10GbE in about 200us with NFS where as over FC you can get it around 50us. Now that's 4x slower on NFS but that's without any disk I/O. If disk I/O is 6.00 ms then adding 0.15ms transfer time is lost in the wash. That on top of the issue that FC is often not that tuned so what could be done in 50us ends up taking 100-150us and is alms the same as NFS.

I've heard of efforts are being made to shorten NFS code path, but don't have details.


NFS is awesome for throughput. It's easy to configure and on things like VMware it is easy to bond multiple NICs. You can even change the config dynamically while the VMs are running.

NFS is already has 100GbE NICs and is shooting for 200GbE next year.

FC on the other hand has just gotten 32G and doesn't look like that will start to get deployed until next year and even then will be expensive.

Analyzing Performance on NFS

If you are having performance issues on NFS and can't figure out why, one cool thing to do is take tcpdump on the receiver as well as sender side and compare the timings. The problem is either the sender, network or receiver. Once you know which the analysis can be dialed in. See


On Tue, Feb 23, 2016 at 12:19 PM, Hameed, Amir <<>> wrote: My two cents based on my experience with running dNFS since 2011. If you have an IO intensive system, you may want to stick with FC. dNFS has been working fine for us for those systems that do not do a lot of throughput, like SOA databases, etc. However, for heavy-duty ERP systems, even though we have implemented 10gbe end-to-end (from hosts to switches to NAS/heads), we are barely meeting the performance. All of our vendors, including Oracle, storage vendor and network vendor looked at their infrastructure for literally months but no one was able to pinpoint where the bottleneck was coming from. We ended up moving two of our Oracle ERP systems back to FC and will move the remaining ERP systems in the near future.

From:<> [<>] On Behalf Of Seth Miller Sent: Tuesday, February 23, 2016 3:02 PM To: Ruel, Chris
Cc:<> Subject: Re: ASM vs. dNFS?


You do not need ASM for OCR and voting disks. These can be on a supported cluster file system or over standard NFS.

You are correct that ASM disk groups are all or nothing for storage snapshots. However, it is not necessary that each database be in its own disk group. For example, I have two databases in the same disk group, I snap the storage of that disk group, mount it up to another server and just delete the files of the other database. This way, you've reduced the management overhead and used the space more efficiently without using any extra space or losing the ability to do snapshots. This addresses points 2 and 3.

It is unclear to me why storage snapshots for ASM disk groups required you to use RDMs. Could you not snap multiple VMDKs at the same time?

All that being said, dNFS has lots of benefits over ASM as well and as I assume you were alluding to, is not mutually exclusive to ASM. NFS in general is obviously much more flexible than ASM including the ability to use CloneDB.

Don't forget that you have a third option which may include just enough of either option to be worth trying, ACFS.

Seth Miller

On Tue, Feb 23, 2016 at 9:35 AM, Ruel, Chris <<>> wrote: This is sort of long so bear with me…

TL;DR: Who has compared ASM vs. dNFS (not used together) and what did you choose and why?

I was wondering if anyone on the list has opinions on, or has evaluated, ASM vs. dNFS in a mutually exclusive configuration for datafile/arch/ctl/redo storage?

We have been using ASM on NetApp over fiber channel for many years now with great success. We particularly like the ability to add/remove spinning disks or SSD on the fly. We can even "upgrade" our filers with no down time by adding in and removing LUNs and letting ASM do it's rebalance thing.

Recently, some new technology changes have become available for us. These changes are in the form of moving our compute platform to UCS/Flexpod environments and the introduction of VMware. Operating on the UCS gives us access to 10gE (currently our infrastructure is primarily 1gE) which brings the option of using dNFS to the table.

Now, I am just starting down the path of comparing the two for pluses and minuses and I do not have all the data yet. Thought I would reach out to the list.

There are a few things that attract us to dNFS:

  1. Less complication…maybe? In RAC environments, I still think we need ASM for OCR/Voting…someone correct me if I am wrong. But, we will not have to manage ASM disk groups like we do now. However, after so many years of using ASM, our team is pretty well versed in it…so, is it really an added complication?
  2. Better ability to use NetApp snapshots:
  3. We can do file level recovery with dNFS which cannot be done with ASM
  4. Right now we have to manage separate disk groups for each database (when we have multiple databases on a node/cluster) if we want to use NetApp snaps since restore is done all-or-nothing at the disk group level. In some cases, we have hit the maximum number of disk groups (63) in ASM. I think multiple disk groups like this also results in more overheard managing and monitoring. Furthermore, more disk groups seems to waste more space as it is sometime hard to predict storage needs…I think in the end the best approach is to over allocate storage instead of having to manage it constantly.
  5. Our primary OS platform is OELinux x86-64. Linux has a LUN path limit of 1024. That sounds like a lot, but, with multiple LUNs per disk group and multipathing in place, each disk group takes up a minimum of 8 LUNs. This is not to mention LUNs supporting the OS and shares. Since we need to have separate disk groups for each database to support snaps, a cluster with a lot of compute power will either hit the LUN path limit or the ASM disk group limit before we run out of compute. My understanding is that we do not have this limit problem with dNFS.
  6. It seems that dNFS will lend itself better to VMware:
  7. Setting up snaps with ASM on VMware led us down the path of using RDM's (which have limits feature wise) instead of VMDK's.
  8. VMDK's with dNFS seems like less configuration which will allow for quicker provisioning on VMware. VMDK's are also the preferred approach according to VMware.
  9. Using ASM and LUNs with VMware still is an issue with the 1024 LUN path limit. However, it moves to the physical hosts in the ESX cluster...not just the guest OS. Therefore, we are seriously limiting the number of guest OS's on our ESX clusters before we run out of compute because will hit the LUN path limit first. So, that's it in a nutshell. I am sure there is a lot more to it but I appreciate any input people may have.



Chris Ruel * Oracle Database Administrator * Lincoln Financial Group<> * Desk:317.759.2172<tel:317.759.2172> * Cell 317.523.8482<tel:317.523.8482>

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Received on Wed Feb 24 2016 - 03:12:34 CET

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