Wednesday , 28 June 2017


Horizon 6 with Virtual SAN: A Big First Step for VDI User Experience

atlantis computing

Gregg Holzrichter

VDI User Experience

Greg Holzrichter, VP of Marketing, Atlantis Computing, says:

The recent release of Horizon 6 was a watershed moment for VMware. They now have a unified platform for desktop and application virtualization that can take full advantage of the Software Defined Data Center. I’m excited about the direction Horizon is heading and VMware’s focus on End User Computing in general. Horizon 6 continues to push the performance envelope with great user experience, lower costs driven by gains in VDI server density, and a cloud-ready approach. But what really sparks my interest is the inclusion of Virtual SAN in Horizon Advanced and Enterprise editions.  Virtual SAN leverages a hyper-converged architecture that works inside of vSphere to pool local solid state drives (SSDs) and hard disk drives (HDDs) from any server including blade servers.  Having Horizon take a strong cut at managing storage with Virtual SAN is a necessary first step towards solving the VDI storage challenge.

Storage continues to be the Achilles Heel of VDI from cost and performance perspective. Implementing the right storage architecture is the single biggest challenge that IT must overcome to deploy virtual desktop environments successfully. Deployment risk, performance, cost, scalability, and high availability are just a few of the storage-related challenges that IT must navigate during a desktop virtualization rollout and conventional storage architectures present only sub-optimal choices.

Traditional storage architectures make it difficult to build virtual desktop environments that get anywhere near to performance expectations at a cost competitive with physical PCs.  Virtual desktop environments, when deployed in large numbers, generate extremely random, very write-intensive IO patterns that slow legacy storage environments considerably. It is this “IO blender effect”, in conjunction with RAID overhead and network latencies that are associated with most virtual infrastructure deployments, that cause legacy storage to underperform badly.

VDI technology has also missed the boat on user expectations.  Targeting the performance level of a circa 2010 desktop PC running WinXP does not help at all with user acceptance of VDI. I have seen any number of deployments hoping to survive on VDI disk performance of 30 IOPS or even much less. Any attempt to provide more than this level requires heavy investment in spinning drives, hybrid arrays, or SSDs to obtain more IO capacity which pushes the per desktop cost of VDI well beyond PC territory.  Many companies have even taken the step of restricting desktop and Outlook search capabilities to reduce IO traffic.  Even after throttling search capabilities, logon time, application launch time, and overall desktop response time will still suffer with significant VDI IOPS restrictions.

To add fuel to the fire, users will compare their new VDI environment with the MacBook Air or Ultrabook that they carry with them everywhere, not with the dust-covered boat anchor PC that has long since disappeared under their desk.  So, we have the CPU performance with VDI to run the OS and applications but a traditional storage architecture that cannot deliver the IOPS to get anywhere close to current PC level performance.  Just look at benchmark studies to see the challenge.  An Apple MacBook Air benchmarks at a PassMark of at least 1100. Ultrabooks, depending on vendor and model, will benchmark in that range as well.  A VDI environment limited to 50 IOPS will only deliver around 17.  Not even close!  Horizon 6 implemented with Virtual SAN changes that equation.  Guess what?  It tests in and around 1100 Disk Mark.  Horizon 6 changes the base level on VDI disk performance.

So all you have to do is deploy Horizon 6 for blazing VDI performance and users will gladly adopt their new virtual desktops.  Why do you need anything else?  The answer is that you do need more for your persistent desktops. Though the IOPS are there, you still need plenty of storage capacity to store all of those unique desktop images. Duncan Epping (see his calculator here) gives us a pretty good idea of how much we need.  Duncan has generated an example for 100 virtual machines with a VM disk size of 50GB with 4GB of memory provisioned, running on a 4 host cluster. The result is a total of 12TB of traditional storage across the 4 hosts plus another 1.2TB of Flash storage. You can do the math for deploying 500, 1000 or even 10000 desktops. That’s a lot of expensive storage and some hefty servers to cram with disks and SSDs. My Atlantis Computing ROI models predict a cost of $117K just for storage for 500 VDI users with Virtual SAN, which translates to $234 per user not including VDI broker, servers, etc.

To get a performant, low cost VDI deployment, Horizon 6 and Virtual SAN needs to be augmented with some kind of storage optimization solution.  This is needed to cut back drastically on the capacity needs for an average VDI environment. When I say drastically, to make VDI cost effective with best possible user experience, we need to cut 60-70% from the cost of storage. This can be only be accomplished by leveraging ALL of the following technologies:

  • In-Memory Storage Optimization — Solution operates as a Virtual Machine in server RAM (not an external appliance.)
  • IO Processing — Manages storage IO in real-time at the compute layer to lower latency and reduce network traffic.
  • Inline De-duplication — Traditional de-duplication is performed in the background on the physical storage AFTER the initial writes are completed. Inline de-duplication is performed in real-time on-the-wire (with no additional latency).
  • IO Blender Fix — Coalesces small random blocks generated by the hypervisor into larger sequential blocks.

There are a number of solutions out there claiming to optimize storage for VDI. You need to find the one that leverages all of the four technologies I identified above and as a result gets cost down to LOWER than PC cost per user, gives you performance headroom and allows the use of smaller form factor servers.

Horizon 6 has taken an important step to get VDI into the performance realm that will make it a real desktop delivery option for any end user.  If storage costs can be managed using the optimization technologies I identified, we will have the perfect solution that can finally bring in large scale VDI adoption.

(Back in February, at VMware Partner Exchange 2014 Atlantis Computing announced a joint solution with VMware that integrated their Virtual SAN capabilities with our own ILIO USX software-defined storage solution. To take this solution directly to Horizon 6, we have just introduced a specific version of ILIO focused on VSAN and VDI. To find out more, check out atlantiscomputing.com)

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