VDI Storage Considerations by Andy Paul, OpenSky Principal Consultant


In July, I had the pleasure of speaking at BriForum in Boston. BriForum is a popular vendor-neutral conference focused on virtualization and mobility technologies. My first session, which was very well received, was titled Where To Stick It: VDI Storage Considerations.

During the session, we focused on three main elements:

  • Storage challenges for VDI deployments
  • Technology options for mitigating those challenges
  • Strategies for mitigating storage challenges

Storage Challenges

Storage design is the most important, and often the most overlooked, aspect for successful virtual desktop delivery. Improperly designed storage can impact the cost, quality, and performance of your VDI solution. Planning storage for VDI is not the same as planning for server virtualization. The workloads, usage patterns, and storage demands for workstation guest operating systems are completely different than server guest operating systems.

During my BriForum session, I polled the 60 attendees to identify those with active VDI deployments. Approximately 40 people raised their hands; of those, over half acknowledged encountering storage issues as part of their VDI environment.

When laying out your storage, you need to consider:

  • Capacity – how much disk space do you need?
  • IOPS – how much throughput is required?
  • Storms – peak utilization periods caused by boot, login, and application launch processes.

In most environments, I see a VDI disk size to range from 8GB to 40GB (on average), with disk usage ranging between 12 and 15 IOPS (on average). However, I’ve seen some peaks of 60-80 GB disk size and 40-50 IOPS per desktop!

The type of VDI environment you are deploying will dictate some of your challenges as well. Do you want to use Persistent or Non-Persistent desktops, or a mix? Do you have processor, disk, or memory intensive applications? Are you using Thin or Thick provisioning?

Storage Technologies

When looking at technology to help mitigate your storage challenges, you should consider:

  • Image Management
  • Deduplication
  • Thin Provisioning
  • Hybrid Solutions
  • Flash-based Array
  • Local Storage
  • Converged Platforms

Of course, capacity is the easiest hurdle to get past. You can always add more capacity, or leverage technologies like thin provisioning and data deduplication, which are standard on most storage platforms; including EMC, IBM, and NetApp solutions.

Hardware appliances, like Atlantis, or software products, like Infinio, sit between the virtual hardware and the storage hardware, providing inline deduplication that reduces the storage and IOPS requirements for write actions. These can also be used to build a cache to effectively speed up IOPS for read operations as well.

Converged storage platforms, such as Nimble, offer adaptive storage arrays; mixing SSD and traditional drives into a common array. Dedicated flash-based arrays, such as Violin, PureStorage, or EMC XtremeIO allow for massive IOPS and memory-based deduplication. However, none of these are the Holy Grail either, just another tool to consider.

I also like to keep local storage in consideration. Local SSD drives can handle large amount of IOPS. Sure, you might not be able to move virtual workloads between servers, but with VDI, do you really need to? You can also extend this localized storage with VMware’s vSAN, HP’s VSA, and GlusterFS; turning those local drives into a distributed storage array.

Finally, there are the hyper-converged platforms, such as Nutanix and Simplivity, which provide an integrated platform for compute and storage. These are scaled linearly by adding additional appliances.

Storage Strategies

There are plenty of non-technical solutions to consider as well. The first, and most critical step, is to assess what you have and define what you need. Determine what your users are actually doing, and what resources they need to do it. This can be done with automated data collection with tools such as Lakeside Software Systrack and Liquidware Labs Stratusphere. But don’t use automation alone. You must also interview users, actively watch and monitor activity, compare to current/actual metrics against similar workloads if possible.

Also, when designing your VDI images, remember a virtual desktop is not the same as a physical one. Trim any unused or unnecessary features and services, and optimize the image to minimize both the storage footprint and the resource utilization.

Antivirus is another area of design consideration. If not properly designed, antivirus solutions can crush your VDI performance. At a minimum, you should stagger your scan schedules to avoid all desktops scanning at the same time. Some organizations may eliminate antivirus in their VDI workloads, others chose to limit scans to memory only, while some may use host-based scanning solutions such as McAfee MOVE or Symantec vShield plugins. While there is no right or wrong antivirus solution, it must be considered and discussed as part of the overall VDI strategy, and its impacts on storage utilization.

Also, consider image management, such as VMware View Linked-Clones, Citrix XenDesktop Machine Creation Services, or Citrix Provisioning Services. Image management can reduced your storage requirements and simplify your VDI environment, especially for non-persistent images.

Tips from the Real World

Tip #1 – Monitor! Monitor and measure your current workloads, as well as future workloads to ensure you are meeting your requirements and avoiding bottlenecks. Tools like Splunk, LoginVSI, and VMTurbo are great for monitoring, assessing, and optimizing your VDI and storage environment.

Tip #2 – Validate vendor claims. Make sure their proposed solution meets your environmental needs, and can scale to match your growth. Beware of the “price per desktop” pitch, as that scale will vary.

Tip #3 – Perform proof-of-concept testing to ensure the proposed solution is as good as it’s cracked up to be and will scale at the forecasted rates.

Tip #4 – It doesn’t really matter what your solution is, as long as it meets your budget and your performance requirements.

Ultimately, there is no magic bullet, there is no one-size fits all solution. However, at OpenSky, we have the tools, experience, and expertise to help you identify and mitigate your VDI storage challenges. To see more on industry trends in VDI, Storage, and Antivirus solutions, check out Project VRC’s State Of the VDI And SBC Union 2014. Also, to see more detail on the planning phases and design considerations, check out my Citrix XenApp 7.5 Desktop Virtualization Solutions book.