Republished: FlexClones or Deduplication?

Author’s Note: This content was first published over at Storage Monkeys, but it appears that it has since disappeared and is no longer available. For that reason, I’m republishing it here (with minor edits). Where applicable, I’ll also be republishing other old content from that site in the coming weeks. Thanks!

I’ve discussed this topic before, but I felt like it was a topic that needed to be revisited again. Storage admins need to know how their choices in storage technologies may or may not impact virtualization efforts, and this particular choice—leveraging pointer-based snapshots or deduplication—is particularly important.

FlexClones Versus Deduplication with VMware Infrastructure

A number of times over the last few months, I’ve run into situations where NetApp’s FlexClone technology was being heavily pitched to customers interested in deploying, or expanding their deployment of, VMware Infrastructure.

In case you aren’t familiar with the use of NetApp FlexClones in conjunction with VMware Infrastructure, have a look at these earlier articles of mine:

How to Provision VMs Using NetApp FlexClones
NetApp FlexClones with VMware, Part 1
NetApp FlexClones with VMware, Part 2
LUN Clones vs. FlexClones

Now, after you’ve read all those articles (you did read them, didn’t you?), it should be fairly clear that using FlexClones can be very advantageous. However, those advantages come with some tradeoffs as well, most notably in the complete and total lack of integration with VMware Infrastructure itself.

This lack of integration means that users can’t use VirtualCenter templates, because the cloning is taking place at the storage array instead of within VMware Infrastructure. This also means that customers can’t apply customization specifications during the cloning process, so users will need to create their own Sysprep answer files and manually Sysprep the VMs before invoking the FlexClone process. Users are required to create scripts and tools to do simple things like using the VM name for the guest OS name during cloning. (Author’s note: many of these issues have been addressed by NetApp’s Rapid Cloning Utility (RCU), which provides some integration into VirtualCenter.)

Deduplication, on the other hand, works seamlessly with VMware Infrastructure. This is primarily because the details of the deduplication are completely hidden; it all occurs “inside the box.” Nothing needs to be configured within VirtualCenter; no VMs need to be modified. The NetApp storage system handles the details of the deduplication process itself, and VMware Infrastructure just consumes the storage.

Looking at these two technologies in that light, one might ask: why use FlexClones at all? If deduplication works seamlessly with VMware Infrastructure and FlexClones don’t, then why bother? To be honest, there are some instances where FlexClones make sense—even with the lack of integration. Consider some of the examples listed below.

  • In instances where a user needs to deploy lots of VMs in a very rapid fashion, FlexClones are much better. If time-to-deployment is the #1 driving factor, then FlexClones are the way to go. This could be particularly applicable and useful in VDI situations, as long as the broker doesn’t mandate handling provisioning itself (like VDM does).
  • In environments where provisioning and re-provisioning occurs on a frequent, regular basis, then FlexClones make sense. Even though large numbers of VMs aren’t being provisioned, the time saved on frequent re-provisioning via FlexClones will not be insignificant.
  • In situtations where there isn’t sufficient storage for the VMs before they are deduplicated, FlexClones may be a better option. Deduplication is post-process, meaning that storage will be needed for the full datasets until deduplication runs. In situations where that isn’t an option, then FlexClones can provide the same end benefit.

Personally, I’m of the opinion that unless an organization meets one of these criteria, then that organization should look to deduplication instead of FlexClones. Of course, that’s just my personal opinion, and I’m open to hear what others have to say about the matter. NetApp gurus, feel free to weigh in.


  1. MThibert’s avatar

    Flexclone has a seamless integration with VMWare SRM. It gives the ability to test your DR without breaking your replication and without using more space (4k Blocks changes only)

  2. Alex Miroshnichenko’s avatar


    You are right about the problems with integrating array based storage services with hypervisor operations.

    The problem with data dedup is that it requires a significant processing power inside the array in order to keep latencies to a minimum level suitable for online storage. Any device capable of such processing would be very expensive – and the practice confirms it. Similar considerations apply to FlexClone functionality – we all know that NetApp is not an inexpensive solution.

    I think there is a lot to be said about a software only implementation of FlexClone like functionality which would be totally storage vendor independent and would allow customers to freely mix different storage devices in the same system. Of course such software solution has to done right not to break performance.


  3. Eric Forgette’s avatar

    Hi Scott,
    Thanks for the author’s note regarding RCU. I would like to clarify though, RCU addresses *ALL* the issues you brought up. I’m not being defensive (thought I am on the team that develops the RCU), I bring this up because the issues you noted were some of the things we set out to address very early on. VMware has provided a rich API which we are able to leverage to provide our customers a truly integrated solution.

    The next version of RCU (with more cool features) will be out soon…
    That was my attempt at marketing a free product. ;-)

    Seriously, with regard to ‘FlexClones versus Deduplication’, you should (with RCU or your own scripts) be able to leverage both. FlexClone will save you time and capacity when you deploy and Deduplication will continue to save you capacity over the life of the VM/Datastore.

    Eric Forgette
    Software Engineer

  4. Jim Taylor’s avatar

    Great job on the present version of RCU.
    Rich B and I went thru it while I was visiting NetApp for the national SE Tech Update a few weeks ago.

    Now that you tempt us with the existence of a new version, Partners get dibs right? ; )


    Jim Taylor
    Senior Systems Engineer

  5. StickerShock’s avatar

    FlexClone sounds great and all, but I just received a quote FlexClone licenses for 2 x N5600 filers and it is coming in at $25K PER FILER. And I have another two filers at my DR site.


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